Ultra-thin, high strength, drug-loaded sutures and coatings thereof

ABSTRACT

Small-diameter suture materials and suture coating materials made from the twisting or braiding of biocompatible polymeric fibers have been developed, which support drug delivery and maintain a high tensile strength. The fibers entrap (e.g., encapsulate) one or more therapeutic, prophylactic or diagnostic agents and provide prolonged release over a period of at least a week, preferably a month. While monofilament fibers lose tensile strength with the inclusion of active agents, twisting the drug-loaded, multifilament fibers allows for an increase in the tensile strength for the overall composites, while still retaining a small diameter. The methods of making these materials and using them for ocular surgery and vasculature repair have also been developed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of and priority to U.S. ProvisionalApplication Nos. 62/307,230 and 62/307,096, both filed on Mar. 11, 2016,which are hereby incorporated herein by reference in their entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with government support under grant numberBGE-1232825, awarded by the National Science Foundation. The governmenthas certain rights in the invention.

FIELD OF THE INVENTION

The present invention relates generally to strong, small-diametersutures for controlled drug delivery, and more particularly, to fibersthat can twist into high-strength sutures or coat sutures.

BACKGROUND OF THE INVENTION

Development of drug-eluting sutures is of significant interest for avariety of clinical applications. Sutures are already used to closewounds or hold tissue together. Delivering active agents at the sametime would promote healing and prevent complications (Casalini, T., etal., International Journal of Pharmaceutics, 429, 148-157 (2012)). Theproblem with many sutures for drug delivery is that incorporation ofagent directly into the suture decreases strength or increases diameterif the agent is incorporated into a coating. (Weldon, C. B., et al., JControl Release, 161, 903-909 (2012)).

Eye infections such as bacterial keratitis and endophthalmitis can leadto significant negative consequences including corneal ulceration,edema, inflammation, and blindness (Lee B J, J Cataract Refract Surg,35, 939-942 (2009)). Conventional nylon sutures used in ocularprocedures can harbor bacteria and potentially facilitate infection(Katz, S., et al., Ann Surg, 194, 35-41 (1981); Leaper, D., et al., AnnR Coll Surg Engl, 92, 453-458 (2010)). This phenomenon is worsened whensutures become loose or break in situ. Almost 40% of loose or brokennylon corneal sutures are contaminated with bacteria, and StaphylococcusEpidermidis is isolated in more than 80% of cases (Heaven, C. J., Eye(Lond), 9 (Pt 1), 116-118 (1995)). It has become routine to prescribeexpensive antibiotic drops off-label for prophylactic use afterophthalmic surgery; however, patients have low compliance using topicaleye drops. Properly instilling eye drops is particularly difficult forpediatric patients and for those who are elderly and/or in cognitivedecline (Winfield, A. J., British Journal of Ophthalmology, 74, 477-480(1990); Burns, E., et al., Age and Ageing, 21, 168-170 (1992)). Up to50% of patients take less than half of the prescribed doses over thecourse of a study on topical antibiotic eye drop compliance (Hermann, M.M., et al., Investigative Ophthalmology & Visual Science, 46, 3832-3832(2005)). Lack of compliance may lead to re-occurrence of an infection orthe development of antibiotic resistance (Bremond-Gignac, D., et al.,Ophthalmol Eye Dis, 3, 29-43 (2011)).

Ophthalmic sutures are commonly used during ophthalmic surgicalprocedures, including trabeculectomy as well as pterygium removal,cataract surgery, strabismus correction surgery, penetratingkeratoplasty, sclerectomy, and conjunctival closure. The choice ofsuture material can strongly impact the occurrence of complicationsrelated to infection and inflammation post ophthalmic surgery, eithercausing irritation and local inflammation or providing a substrate formicroorganism growth. The suture materials typically employed includenon-biodegradable ophthalmic suture materials such as ETHILON® nylonsuture, MERSILENE® polyester fiber suture, PERMA-HAND® silk suture,PROLENE® polypropylene suture, each commercially available from Ethicon,Somerville, N.J.; and VASCUFIL® coated monofilament suture composed of acopolymer of butylene terephthalate and polyteramethylene ether glycol,MONOSOF^(˜)DERMALON® monofilament nylon sutures composed of long-chainaliphatic polymers Nylon 6 and Nylon 6.6, NOVAFIL® monofilament suturescomposed of a copolymer of butylene terephthalate and polyteramethyleneether glycol, SOFSILK® braided sutures composed of fibroin,TI-CRON-SURGIDAC® braided polyester sutures composed of polyesterterephthalate, SURGILON® braided nylon sutures composed of thelong-chain aliphatic polymers Nylon 6 and Nylon 6.6 and SURGIPROII-SURGIPRO® sutures composed of polypropylene, each commerciallyavailable from U.S. Surgical, Norwalk, Conn.

Ideally, ophthalmic suture materials are biodegradable and biodegradableover the useful suture lifetime, retaining the requisite tensilestrength and capable of delivering therapeutic or prophylactic agents toincrease patient success. For pterygium removal, cataract surgery andstrabismus correction surgery, sutures could be used to close the woundand release antibiotic and anti-inflammatory drugs. For trabeculectomysurgeries, sutures could be placed on sclera flaps providing localchemotherapeutic agents, decreasing production of scar tissue, and onconjunctival closure with antibiotic release. In penetratingkeratoplasty, the sutures hold the graft, as well as release antibioticand immunosuppressant or anti-inflammatory agents.

An alternative to frequent topical applications would be to supplyantibiotics directly from the surgical suture. For this purpose, thesuture needs to (i) be of suitable size, (ii) be of high-strength toresist breakage and bacterial colonization, and (iii) supply aneffective amount of antibiotic.

However, clinical implementation of sutures has been limited due to theinability for drug-loaded sutures to meet United States Pharmacopeia(U.S.P.) standards for suture strength (Pruitt L A, et al., MRSBulletin, 37, 698 (2012); Kashiwabuchi F, et al., Translational VisionScience & Technology, 6, 1 (2017)). Conventional suture manufacturingprocesses are not compatible with most therapeutic moieties, anddrug-loaded sutures in preclinical development have demonstratedbreaking strengths up to ten folds less than the strength required forclinical use (Hu W, et al., Nanotechnology, 21, 315104 (2010);Padmakumar S, et al., ACS Applied Materials & Interfaces, 8, 6925(2016)). Attempts to develop drug-eluting sutures have been limited bylack of sufficient tensile strength (especially with the inclusion ofdrugs), poorly sustained drug release, or lack of scale needed forcommercial viability (Wen Hu, et al., Nanotechnology, 21, 1-11 (2010);Pasternak, B., et al., Int J Colorectal Dis, 23, 271-276 (2008);Obermeier, A., et al., PLoS One, 9, e101426 (2014); Morizumi, S., etal., Journal of the American College of Cardiology, 58, 441-442 (2011);Mack, B. C., et al., J Control Release, 139, 205-211 (2009); Lee, J. E.,et al., Acta Biomater, 9, 8318-8327 (2013); Joseph, J., et al., NanoLetters, 15, 5420-5426 (2015); Hu, W., et al., Nanotechnology, 21,315104 (2010); Hu, W., et al., Society of Chemical Industry, 59, 92-99(2010); He, C. L., et al., J Biomed Mater Res A, 89, 80-95 (2009);Catanzanoa, O., et al., Materials Science and Engineering: C, 43,300-309 (2014); Choudhury, A. J., et al., Surgery, doi:10.1016/j.surg.2015.07.022. Epub Aug. 29 (2015)).

Although nylon sutures are used in more than 12 million procedures peryear globally to close ocular wounds and incisions, no drug-elutingsutures have been approved for ophthalmic use (Kronenthal R, P., et al.,Sutures Materials in Cataract Surgery, (1984); Grinstaff, M. W.,Biomaterials, 28, 5205-5214 (2007)). In 2002, Ethicon received approvalto market a series of antibiotic-coated sutures. However, they are onlyavailable in sizes #1-0-#6-0, according to the United StatesPharmacopeia (U.S.P.), and none were indicated for ophthalmic use.Ophthalmic sutures require sizes #8-0-#10-0 or thinner, and to date, nomarket offering is available for antibiotic-eluting sutures for ocularsurgery (Marco F, et al., Surg Infect (Larchmt), 8(3), 359-365 (2007);Ming, X., et al., Surg Infect (Larchmt), 8, 209-214 (2007); Ming, X., etal., Surg Infect (Larchmt), 8, 201-208 (2007); Ming X, et al., SurgInfect (Larchmt), 9, 451-458 (2008)). Certain electrospun fibers weredeveloped with a capability of drug loading (US 2013-0296933), but it isunclear how to maintain a tensile strength that satisfies the clinicalstrength requirement for sutures and is not compromised with drugloading. Due to this challenge drug-eluting sutures have been limited todrug-eluting coatings. While this method does not affect suturestrength, it limits the amount of drug that can be included and resultsin rapid drug release as opposed to the sustained drug release neededfor clinical applications outside of anti-infection uses. It is furtherdesired to develop sutures capable of releasing any other type of drugfor any other surgical application at any size.

Therefore, it is an object of the present invention to provideultra-thin (small diameter), high strength multifilament compositefibers that are capable of eluting drugs in a controlled manner, withoutdecreasing the tensile strength.

It is another object of the present invention to provide activeagent-eluting sutures as substitutes for nylon (permanent) or VICRYL®(absorbable) sutures used in ophthalmic surgeries such as cataract,corneal transplant, injury, or in other specialty surgeries, supportingadditional therapeutic functionality.

It is yet another object of the present invention to provide controlledcoatings on existing sutures to add functionality such as elution of oneor multiple drugs.

SUMMARY OF THE INVENTION

Suture materials or suture coating materials made from twisted,biocompatible polymeric fibers with high tensile strength for use insurgical repair and drug delivery have been developed. A plurality offibers (e.g., electrospun fibers) is twisted or braided in a bundle toform a multifilament suture, or twisted or braided around a thread orsuture to form a multifilament coating. The twisting increases thetensile strength of the overall multifilament composite, even in thepresence of one or more active agents entrapped in the fibers.Orientation of polymer chains through molecular confinement, thusforming nanostructures, also enhances polymer crystallinity andstrength. While a mono-filament fiber of a certain diameter loses itstensile strength significantly with the inclusion of therapeutic,prophylactic or diagnostic agents (e.g., 8 wt % levofloxacin), twistingof multiple (e.g., hundreds) fibers containing the drug into amultifilament composite of a similar diameter precludes the loss intensile strength normally associated with drug loading. Additionaltwisting of these fibers serves to further increase the strength of themultifilament composite.

The fibers can be micro-fibers or nano-fibers. The twisted multifilamentcomposite can have a diameter of less than 50 μm, less than 40 μm, andpreferably less than 30 μm. For a multifilament composite having adiameter between 20 μm and 29 μm and optionally containing an activeagent, the tensile strength of the composite should be greater than 0.24N while satisfying the size and strength requirements for a #10-0 sutureaccording to United States Pharmacopeia. For a multifilament compositehaving a diameter between 30 μm and 39 μm and optionally containing anactive agent, the tensile strength of the composite should be greaterthan 0.49 N and the composite satisfies the size and strengthrequirements for a #9-0 suture according to United States Phaimacopeia.For a multifilament composite having a diameter between 40 μm and 49 μmand optionally containing an active agent, the tensile strength of thecomposite should be greater than 0.69 N and the composite satisfies thesize and strength requirements for a #8-0 suture according to UnitedStates Pharmacopeia.

The multifilament sutures generally maintain at least about 95%, 90%,85%, or 80% of their mechanical properties (e.g., breaking strength)even after immersion in an aqueous environment for about 1 week, 2weeks, 30 days, 45 days, or greater. One or more therapeutic,prophylactic and/or diagnostic agents can be included, up to about 24 wt% or greater in the multifilament composite as a drug-releasing suturewithout compromising the tensile strength as required by United StatesPharmacopeia. The multifilament composites generally have a diametersuitable for ophthalmic suturing procedures. The multifilamentcomposites can also be twisted around a thread to provide drug-elutionfunctionality, where the overall size of the coated suture stillsatisfies the needs for ophthalmic suturing procedures.

Exemplary suture formulation includes multi-nanofiber filaments madefrom polymers such as polyhydroxy acids such as poly(lactic-co-glycolicacid), polylactide, and polyglycolide, polydioxanone, polycaprolactone,or a copolymer, blend, or mixture thereof. A preferred sutureformulation is made from degradable, drug-loaded polymeric multifilamenttwisted fibers, surpassing U.S.P. specifications for suture strengths.The suture may be of variable sizes from 2-0 to 10-0 U.S.P.specifications, based on the parameters in operating fabricationtechniques (e.g., electrospinning) and the twisting and/or braidingparameters of filaments. The suture may be formulated to degrade in vivoover a time period from a few days to a few years. Suitable solvents forthe polymers include chloroform, methanol, acetone,hexafluoroisopropanol, or other solvent depending on the solubility ofspecific polymers. In one embodiment, the suture materials and thecoating materials for sutures are made from a polyhydroxy acid such aspolylactide, polyglycolid, or a copolymer thereof or polycaprolactone,and optionally a polyalkylene oxide such as poly(ethylene glycol) or apolyalkylene oxide block copolymer. The sutures entrap (e.g.,encapsulate) one or more therapeutic, prophylactic or diagnostic agentsand provide prolonged release over a period of at least a week,preferably a month.

In some embodiments, s semi-crystalline, hydrophobic, degradablepolymer, polycaprolactone (PCL) is used. Its fiber crystallinity, andtherefore suture tensile strength, is maximized through the nanofiberfabrication process of low molecular weight PCL and subsequent twistingto form single sutures with additional compaction and structuralreinforcement. Electro spinning may alter the molecular orientation ofPCL to improve crystallinity. The molecular confinement may contributeto the increase in tensile strength of PCL nanofibers even with reduceddiameter.

The degradable, multifilament sutures meet U.S.P. specifications forsize and strength suitable for ophthalmic use, and surpass breakingstrength specifications when loaded with a wide range of antibiotics ofdifferent physicochemical properties. Unlike micron-sized, electrospunPCL monofilament sutures which lose more than 50% of their strength withinclusion of antibiotics such as levofloxacin, the twisted bundle of aplurality of nanofibers, forming micron-wide sutures, generally do notlose strength with inclusion of an equivalent amount of levofloxacin.The multifilament sutures exhibit biocompatibility comparable toconventional nylon sutures, and are able to deliver active agent (e.g.,levofloxacin) at detectable levels in eyes for at least 10, 12, 14, 16,18, 20, 30 days, or longer. The antibiotic-eluting, multifilamentsutures are generally able to prevent ocular infection and decreasebacterial load against one or multiple bacterial challenges for a periodof about 1 week, 2 weeks, or longer in vivo, significantly moreeffective than a single post-operative antibiotic drop.

Exemplary therapeutic or prophylactic agents include, but are notlimited to, anti-inflammatory agents such as dexamethasone,prednisolone, triamcinolone, and flurbiprofen, released in an effectiveamount to prevent post-operative inflammation resulting from theophthalmic procedure or from the presence of the suture. Othertherapeutic agents include rapamycin, neomycin, polymyxin B, bacitracin,gramicidin, gentamicin, oyxtetracycline, ciprofloxacin, ofloxacin,miconazole, itraconazole, trifluridine, and vidarabine to prevent orinhibit a disease or disorder. Sutures release anti-infective agentssuch as levofloxacin for a period of at least seven days, morepreferably 30 days, in an effective amount to prevent or treatinfection. The released drug from the multifilament suture itself maytreat an infection that a common suture procedure is at high risk ofdeveloping or further developing.

In another embodiment, the drug-loaded, multifilament nanofibers mayweave around and serve as a drug-eluting thin coating on existing orother commercially available sutures. The coating thickness is tunable,and the overall size of the multi-nanofiber-coated suture still meetsU.S.P. size requirements.

The multifilament suture can be further coated with one or morematerials for lubrication, glideability, permeation or impermeation,wettability, and/or non-fouling purposes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of the electrospinning configuration to make andtwist electrospun fibers.

FIG. 2 is a bar graph showing the breaking strengths (N) of twistedmultifilaments (all with 1,575 twists, and 28 μm in diameter) formedwith electrospun fibers of different polymers. (* p<0.05; conditionswith different numbers of asterisks are statistically different withp<0.05. Conditions with an equivalent number of asterisks are notstatistically different.) The dash line indicates the standards forsutures of USP size 10-0. Polymers used include polycaprolactone (PCL),polylactic acid (PLA), poly (lactide-co-glycolide) 75:25 (PLGA 75:25),polyglycolide (PGA), and polydioxanone (PDO).

FIGS. 3A-3E show the preparation and characterizations of monofilamentfibers. FIG. 3A is a schematic of electrospinning configuration to makemonofilament fibers. FIG. 3B is a bar graph showing the diameter (m) ofmonofilament electrospun fibers forming from poly (L-lactic acid) (PLLA)solution containing levofloxacin and different amounts of polyethyleneglycol (PEG) at 1%, 2%, or 4%, or 2% F127. FIG. 3C is a bar graphshowing the breaking strength (N) of the monofilament fibers of FIG. 3B.FIG. 3D is a line graph showing the in vitro release of levofloxacinfrom the monofilament fibers of FIG. 3B. FIG. 3E is a scatter plotshowing the area size of the inhibition zone (cm²) against S.Epidermidis by the monofilament made containing 4% PEG over time (days)in vitro.

FIG. 4 is a bar graph showing the breaking strengths (N) of twistedmultifilaments formed with polycaprolactone (PCL) of different molecularweights, or with PCL and 8 (w/w) % levofloxacin (PCL/Levo). (Conditionswith different numbers of asterisks are statistically different withp<0.05. ## indicates statistical significance at p<0.01.) FIG. 5 is abar graph showing the breaking strengths (N) of twisted multifilamentsformed with different amounts of polycaprolactone (PCL) containing 8 wt% levofloxacin (PCL/Levo).

FIGS. 6A, 6B, and 6C are bar graphs showing the breaking strengths (N)of twisted multifilaments having different diameters, 21 μm, 28 μm (FIG.6A), 38 μm (FIG. 6B), and 48 μm (FIG. 6C). The fibers were formed withPCL and optionally containing 8 (w/w) % levofloxacin.

FIG. 7 is bar graph showing the breaking strengths (N) of PCLmultifilaments of various twists, and the filaments optionally contain 8(w/w) % levofloxacin. (Conditions with different numbers of asterisksare statistically different to each other with p<0.05. Conditions withan equivalent number of asterisks are not statistically different.)

FIG. 8 is a bar graph showing the breaking strengths (N) ofmultifilaments, all 28 μm in diameter, containing different amounts (wt%) of levofloxacin.

FIG. 9 is bar graph showing the breaking strengths (N) ofmultifilaments, all 28 μm in diameter and having 1,575 twists,containing different drugs at 8 (w/w) %.

FIG. 10 is a line graph showing the cumulative release of levofloxacin(μg) over time (hr) in 37° C. phosphate buffered saline from a 15-mmlong, PCL/Levo twisted multifilament of 28 μm in diameter.

FIG. 11 is a schematic of the electrospinning configuration to coat asuture with electrospun fibers. “d” refers to the distance between thedrill chuck 370 and the standalone, grounded collector 302.

FIG. 12 is a bar graph showing the amounts of bacteria (colony formingunits, CFU), at 48 hours after suture implantation and bacterialadministration (except untreated rat cornea) in Sprague-Dawley ratcornea, of different types of sutures. The rats' corneas were eitherhealthy, untreated (no suture implantation nor bacterial administration)or implanted with the following sutures and treatments: (i) VICRYL®suture, no antibiotic; (ii) nylon suture, no antibiotic; (iii) nylonsuture and a single drop of 0.5% levofloxacin immediately followingimplantation of the suture; (iv) nylon suture and a prescribed, daily,3-drop of 0.5% levofloxacin; (v) nylon suture that was coated with PCLmultifilament fibers containing 8% levofloxacin (PCL/Levo/Nylon), and(vi) sutures made from multifilament fibers electrospun from PCLsolution containing 8% levofloxacin (PCL/Levo). Conditions withdifferent numbers of asterisks are statistically different from eachother with p<0.05. Conditions with an equivalent number of asterisks arenot statistically different.

FIGS. 13A and 13B are graphs showing the amounts of bacteria (colonyforming units, CFU) at day 7 (FIG. 13A) and the percent of rat corneaswithout infection over 7 days (FIG. 13B), in Sprague-Dawley rat corneaimplanted with (1) Nylon sutures on day 0 and administered with S.aureus on day 5 only, (2) 10-0 grade multifilament sutures made frompolycaprolactone (PCL) containing 8% levofloxacin (PCL/8%) andadministered with S. aureus on day 0 following suture implantation andon day 5, (3) 10-0 grade multifilament sutures made frompolycaprolactone (PCL) containing 16% levofloxacin (PCL/8%) andadministered with S. aureus on day 0 following suture implantation andon day 5, or (4) no suture implantation nor bacterial administration(control, untreated).

FIG. 14 is a bar graph showing the thickness of neointimal hyperplasia(μm) at the anastomosis site of rat's abdominal aorta, at two weeks,after the vessels were tied together using, (i) 8-0 nylon suture, (ii)nylon suture coated with PLLA/PEG containing 20% rapamycin (8-0), or(iii) nylon suture coated with PLLA/PEG containing 40% rapamycin (8-0).Data are calculated as means±SEM. ** denotes p<0.01.

FIG. 15 is a line graph showing the cumulative release of rapamycin (μg)over time (days) in vitro from rapamycin-loaded (at 20%, 40%, or 80%)nanofibers coated around an existing suture.

FIG. 16 is a bar graph showing the breaking strengths (N) of variousNylon sutures coated with rapamycin-loaded (at 20%, 40%, or 80%)PLLA/PEG nanofibers.

DETAILED DESCRIPTION OF THE INVENTION I. Definitions

The term “nanofiber” herein refers to a fiber of material with athickness or diameter in the range of 1 nm to 1000 nm, while the lengthmay be in the nanometer, micron, or millimeter range or greater. Theterm “filament” herein refers to a slender threadlike object, or inrelevant sections refers to the disclosed nanofiber; whereas“multi-filament” refers to a plurality of filaments or the disclosednanofibers, in a bundle.

The term “suture” herein refers to a thread or wire used to jointogether a wound or surgical incision. The disclosed multi-filamentsuture generally refers to a bundle of twisted nanofibers serving as thethread that may be attached or otherwise secured to a needle and be usedby physicians or other medical professionals to join together wounds orincisions in surgery.

The term “electrospinning” refers to a technique that employs electricforces to elongate and decrease the diameter of a viscoelastic polymerstream, allowing for the formation of solid fibers ranging fromnanometers to microns in diameter.

The term “grounded” generally refers to the status of connection to aground. In electrical engineering, ground or earth is the referencepoint in an electrical circuit from which voltages are measured, acommon return path for electric current, or a direct physical connectionto the Earth. Therefore “grounded” as used herein in relation toelectrospinning refers a collector acting as an electrode that isconnected to ground or earth, as compared to a positive electrode (e.g.,a charged needle tip or nozzle).

The term “collector” as used herein refers to a device whereelectrically charged solution, jet, melt, or gel is deposited onto in anelectric field. Generally the collector is grounded, so as to provide agrounded electrode (that is apart from a positive electrode (e.g.,electrically charged needle tip or nozzle)). The “collector” may alsorefer elements that attach or connect to the device where electricallycharged solution, jet, melt, or gel is deposited onto, where the wholeis electrically connected and grounded.

The term “chuck” as used herein refers to a type of clamp used to holdan object with radial symmetry (e.g., a cylinder), and herein may bemechanically and electrically connected via an adaptor to a rotator, informing a part of a grounded collector. For examples, in drills, a chuckholds the rotating tool or workpiece.

The term “alkyl” refers to the radical of saturated aliphatic groups,including straight-chain alkyl groups, branched-chain alkyl groups,cycloalkyl (alicyclic) groups, alkyl-substituted cycloalkyl groups, andcycloalkyl-substituted alkyl groups.

In preferred embodiments, a straight chain or branched chain alkyl has30 or fewer carbon atoms in its backbone (e.g., C1-C30 for straightchains, C3-C30 for branched chains), preferably 20 or fewer, morepreferably 15 or fewer, most preferably 10 or fewer. Likewise, preferredcycloalkyls have from 3-10 carbon atoms in their ring structure, andmore preferably have 5, 6 or 7 carbons in the ring structure. The term“alkyl” (or “lower alkyl”) as used throughout the specification,examples, and claims is intended to include both “unsubstituted alkyls”and “substituted alkyls”, the latter of which refers to alkyl moietieshaving one or more substituents replacing a hydrogen on one or morecarbons of the hydrocarbon backbone. Such substituents include, but arenot limited to, halogen, hydroxyl, carbonyl (such as a carboxyl,alkoxycarbonyl, formyl, or an acyl), thiocarbonyl (such as a thioester,a thioacetate, or a thioformate), alkoxyl, phosphoryl, phosphate,phosphonate, a hosphinate, amino, amido, amidine, imine, cyano, nitro,azido, sulfhydryl, alkylthio, sulfate, sulfonate, sulfamoyl,sulfonamido, sulfonyl, heterocyclyl, aralkyl, or an aromatic orheteroaromatic moiety.

Unless the number of carbons is otherwise specified, “lower alkyl” asused herein means an alkyl group, as defined above, but having from oneto ten carbons, more preferably from one to six carbon atoms in itsbackbone structure. Likewise, “lower alkenyl” and “lower alkynyl” havesimilar chain lengths. Throughout the application, preferred alkylgroups are lower alkyls. In preferred embodiments, a substituentdesignated herein as alkyl is a lower alkyl.

It will be understood by those skilled in the art that the moietiessubstituted on the hydrocarbon chain can themselves be substituted, ifappropriate. For instance, the substituents of a substituted alkyl mayinclude halogen, hydroxy, nitro, thiols, amino, azido, imino, amido,phosphoryl (including phosphonate and phosphinate), sulfonyl (includingsulfate, sulfonamido, sulfamoyl and sulfonate), and silyl groups, aswell as ethers, alkylthios, carbonyls (including ketones, aldehydes,carboxylates, and esters), —CF3, and —CN. Cycloalkyls can be substitutedin the same manner.

The term “mechanical strength”, as used herein, refers to any one ofultimate tensile strength (maximum stress bared until failure (N)), peakload, load at yield (breaking strength) (N), tenacity, initial stiffness(N/mm), or the modulus of elasticity (Young's modulus). The modulus ofelasticity measures an object or substance's resistance to beingdeformed elastically (i.e., non-permanently) when a force is applied toit. The elastic modulus of an object is defined as the slope of itsstress-strain curve in the elastic deformation region. It can bemeasured using the following Formula: E=Stress/Strain, where Stress isthe force causing the deformation divided by the area to which the forceis applied and Strain is the ratio of the change in some lengthparameter caused by the deformation to the original value of the lengthparameter. The modulus of elasticity is presented in Pascals (Pa), ormegapascals (MPa). The term “attached”, as used herein, refers to theconnection of elements in a system, generally via a mechanical meansincluding, but not limited to, a clamp, a claw, a clip, an interlock, ascrew, a magnetic attraction, an adhesive, or a vacuum suction. In someembodiments, “attached” can refer to elements that are already anintegral piece of a whole device. It is interchangeable with “connected”as used herein.

The term “inhibit,” “inhibiting,” or “inhibition” refers to a decreasein activity, response, condition, disease, or other biologicalparameter. This can include but is not limited to the complete ablationof the activity, response, condition, or disease. This may also include,for example, a 10% reduction in the activity, response, condition, ordisease as compared to the native or control level. Thus, the reductioncan be a 10, 20, 30, 40, 50, 60, 70, 80, 90, 100%, or any amount ofreduction in between as compared to native or control levels.

The term “prodrug”, as used herein, refers to compounds which, underphysiological conditions, are converted into the therapeutically activeagents of the present invention. A common method for making a prodrug isto include selected moieties which are hydrolyzed under physiologicalconditions to reveal the desired molecule. In other embodiments, theprodrug is converted by an enzymatic activity of the host animal.

The term “prevent,” “preventing,” or “prevention” does not requireabsolute forestalling of the condition or disease but can also include areduction in the onset or severity of the disease or condition orinhibition of one or more symptoms of the disease or disorder.

The term “treat” or “treatment” refers to the medical management of asubject with the intent to cure, ameliorate, stabilize, or prevent adisease, pathological condition, or disorder. This term includes activetreatment, that is, treatment directed specifically toward theimprovement of a disease, pathological condition, or disorder, and alsoincludes causal treatment, that is, treatment directed toward removal ofthe cause of the associated disease, pathological condition, ordisorder. In addition, this term includes palliative treatment, that is,treatment designed for the relief of symptoms rather than the curing ofthe disease, pathological condition, or disorder; preventativetreatment, that is, treatment directed to minimizing or partially orcompletely inhibiting the development of the associated disease,pathological condition, or disorder; and supportive treatment, that is,treatment employed to supplement another specific therapy directedtoward the improvement of the associated disease, pathologicalcondition, or disorder.

The term “therapeutic agent” refers to an agent that can be administeredto prevent or treat one or more symptoms of a disease or disorder. Thesemay be a nucleic acid, a nucleic acid analog, a small molecule, apeptidomimetic, a protein, peptide, carbohydrate or sugar, lipid, orsurfactant, or a combination thereof.

The term “diagnostic agent”, as used herein, generally refers to anagent that can be administered to reveal, pinpoint, and define thelocalization of a pathological process.

The term “prophylactic agent”, as used herein, generally refers to anagent that can be administered to prevent disease or to prevent certainconditions like pregnancy.

The phrase “pharmaceutically acceptable” refers to compositions,polymers and other materials and/or dosage forms which are, within thescope of sound medical judgment, suitable for use in contact with thetissues of human beings and animals without excessive toxicity,irritation, allergic response, or other problem or complication,commensurate with a reasonable benefit/risk ratio. The phrase“pharmaceutically acceptable carrier” refers to pharmaceuticallyacceptable materials, compositions or vehicles, such as a liquid orsolid filler, diluent, solvent or encapsulating material involved incarrying or transporting any subject composition, from one organ, orportion of the body, to another organ, or portion of the body. Eachcarrier must be “acceptable” in the sense of being compatible with theother ingredients of a subject composition and not injurious to thepatient.

The term “biodegradable” as used herein, generally refers to a materialthat will degrade or erode under physiologic conditions to smaller unitsor chemical species that are capable of being metabolized, eliminated,or excreted by the subject. The degradation time is a function ofcomposition and morphology. Degradation times can be from hours toyears.

The term “biocompatible” as used herein, generally refers to materialsthat are, along with any metabolites or degradation products thereof,generally non-toxic to the recipient, and do not cause any significantadverse effects to the recipient. Generally speaking, biocompatiblematerials are materials which do not elicit a significant inflammatoryor immune response when administered to a patient.

The term “degrade”, as used herein, refers to a reduction in one or moreproperties of the polymer over time. The one or more properties includethe molecular weight, total mass, mechanical strength, elasticity, orthe density or porosity of the fibers formed from polymers. Generally, adegradable polymer is capable of being absorbed by living mammaliantissue. This can occur over a period of days, weeks, months, or years.The prevailing mechanism of degradation of hydrolytically biodegradablepolymers is chemical hydrolysis of the hydrolytically unstable backbone.In a bulk eroding polymer, the polymer network is fully hydrated andchemically degraded throughout the entire polymer volume. As the polymerdegrades, the molecular weight decreases. The reduction in molecularweight is followed by a decrease in mechanical properties (e.g.,strength) and scaffold properties. The decrease of mechanical propertiesis followed by loss of mechanical integrity and then erosion or massloss (Pistner et al., Biomaterials, 14: 291-298 (1993)). Non-degradablepolymer is suitably resistant to the action of living mammalian tissue.A similar distinction between non-absorbable and absorbable sutures areused by the United States Pharmacopeia (U.S.P.).

Use of the term “about” is intended to describe values either above orbelow the stated value in a range of approximately +/−10%. The precedingranges are intended to be made clear by context, and no furtherlimitation is implied.

II. Methods to Make Sutures or Coating for Sutures

1. Twisting and Braiding of Fibers Using Electrospinning

Electrospinning is a versatile technique first introduced in the early1900's, which employs electric forces to elongate and reduce thediameter of a viscoelastic polymer jet, allowing for the formation ofsolid fibers ranging from nanometers to microns in diameter (Bhardwaj,N., et al., Biotechnol Adv, 28, 325-347 (2010); Li, D. & Xia, Y.,Advanced Materials, 16, 1151-1170 (2004)). An electrostatic charge isapplied on the needle to overcome the surface tension of the solution.Usually, the concentration of the polymer solution in electrospinning isgreater than a minimum concentration for any given polymer, termed thecritical entanglement concentration, below which a stable jet cannot beachieved and no nanofibers will form, although nanoparticles may beachieved (electrospray) (Leach M K, et al., J Vis Exp., (47): 2494(2011)). The multifilament composite fibers built upon electrospinning,are twisted or braided to form ultra-thin, high strength, drug-loadedsutures or to coat a commercially available suture or thread to provideadditional therapeutic functionality.

A. Twisting

As shown in FIG. 1, some embodiments provide that the charged polymerjet deposits in the air gap between a chuck 270 (grounded) and anotherparallel, grounded collector 202. Even when the chuck is attached toneedles or substrates that protrude into the air gap between the chuckand the parallel collector, charged polymer jets can deposit in between,where fibers are formed with one end attached to the chuck and the otherend attached to the standalone parallel collector. In a generalconfiguration, collectors capable of rotation are used for polymer jetsto deposit and form fibers.

In another embodiment, a suture, thread or equivalent that is conductiveor non-conductive, which can be any commercially available suture, isplaced between a drill chuck 370 and a parallel stand 302, where thethread end of the suture is fixed at the drill chuck 370 and the needleend is placed through the stand 302 but kept free to rotate, as shown inFIG. 11. This configuration allows for the deposition of hundreds offibers around the suture between the chuck 370 and the parallel stand302. Due to the electric charge, the fibers are held tightly by thechuck and the parallel stand. Rotating the drill chuck twists thefibers, with the suture “buried” among the fibers, to form nanofibercoating on the suture.

The individual fibers can be so thin that they are able to align theinternal polymer chains without the use of heat treatment or extrusionto provide increased strength.

In some embodiments, when the parallel collector is also connected to amotor or is a second drill chuck that is connected to a motor, the chuckcan rotate in one direction, e.g., clockwise, to twist these fibers,while the other end is held stationary on the parallel collector. Inother embodiments, both ends of the fiber(s) (e.g., in oppositedirections, or at different speed) are rotated to twist the fibers.

The twisted fibers can optionally be further twisted in the oppositedirection, e.g., counterclockwise, to ensure that the twisted fibers donot coil or snap.

When a drill chuck is rotated 360° relative to the opposing collector,one twist is done to the fiber(s). To form densely twisted fibers ofsufficient strength, hundreds, thousands or tens of thousands of twistscan be done to the fibers. For instance, when the distance between thedrill chuck and the opposing collector is about 50 cm, 60 cm, 70 cm, 80cm, 90 cm, or 100 cm, twists of increasing numbers can be done to thefibers, e.g., 500 twists, 1,000 twists, 1,500 twists, 2,000 twists,2,500 twists, 3,000 twists, 3,500 twists, and 4,000 twists,respectively, or even greater. As the number of twists increases, thediameter of the overall fiber bundle generally decreases, and thestrength generally increases.

Even when drug loading decreases the strength of individual fibers,twisting the fibers reduces the loss of tensile strength or evenincreases the strength for the multifilament composite. The number oftwists needed to meet certain strength parameters will vary depending onthe composition of the polymer/drug, and the size of individual fibers.For instance, with fibers made from a high molecular weight (e.g., 220kDa) poly (L-lactic acid) (PLLA), twists ranging from 2,000 to 4,000 aregenerally needed to generated twisted fibers that meet the strengthrequirement for sutures according to United States Pharmacopeia (USP).Alternately, certain types of polycaprolactone (PCL), with or withoutcertain drugs, can be twisted at a lower number, e.g., much below 1,575twists, and still surpass strength requirements. One can increase thenumber of twists and decrease the diameter while maintaining strength.In some embodiments, including therapeutic, prophylactic or diagnosticagents up to about 5%, 10%, 15%, 20%, 25%, 30% by weight or evengreater, can still meet USP requirements for strength.

Picking highly crystalline polymers and using predominantly nanofiberswhich have more aligned polymer chains and greater individual tensilemodulus, then twisting these to make them stronger and more imperviousto damage are key to producing small diameter very strong fibers. Giventhe high crystallinity and aligned polymer chains of a nanofiber, andpotentially the hydrophobicity, the agents move to the outside/surfaceof each nanofiber rather than being mixed in with the polymer chains andpolymer matrix, which would lead to decreased strength and is whathappens to micron-sized monofilaments.

B. Braiding

A braid is an organization of three or more fibers or fiber bundlesintertwined in such a way that no two fibers (or fiber bundles) aretwisted around one another. In one embodiment, fibers are removed fromthe collector(s) and placed into braiding machines known in the art toform braids of fibers. The electrospinning system twists rather thanbraids. Several composite fibers can be collected and attached to thedrill chuck and/or to a standstill or rotating parallel stand and thedrill chuck rotated to twist the composite fibers together in the sameway that individual nanofibers are twisted together to manufacture thecomposite fiber.

A component of a system for removing a fiber from a collection surfaceneeds not be in the illustrated form. Any suitable component can beincluded to remove the fibers such as, without limitation, a blade, awedge, a plate, or any other shaped device that can shear or cut thefiber from the collection surface.

In some embodiments, multiple 10-0 and/or 11-0 nanofiber sutures may bebraided to make drug-loaded sutures that meet U.S.P. specifications for2-0-7-0 sutures.

2. Configuration of Electrospinning Apparatus

Generally, the parallel collectors are in a lined up in a position thatis perpendicular to the needle or nozzle. The needle or nozzle can be90°, 85°, 80°, 75°, 70°, 65°, 60°, 55°, 50°, 45°, 40°, 35°, 30°, or atanother non-parallel angle with respect to the collectors. The distancebetween the end of a needle or the tip of a nozzle and the collectorscan be between about 4 cm and about 100 cm, or even greater. In someembodiments, this distance is between about 6 cm and about 25 cm.

The distance between the motor and the parallel stand (d) can be betweenabout 2 mm up to about 200 cm, or even greater, e.g. distances between270 and 202 in FIG. 1, or between 370 and 302 in FIG. 11. Maximumpossible distance is generally understood to be related to fiberdiameter, as well as other formation parameters. In some embodiments,the distance between the collectors is between about 15 cm and about 35cm.

Generally, the heights of the collectors are about the same, i.e.,parallel collectors. In other instances, the heights of the opposingcollectors can be of different heights, by difference of 10%, 20%, 30%,40% or greater, of the taller collector.

A polymer solution, sol-gel, suspension or melt may be loaded into theelectrospinning ejection device (e.g., needled syringe, nozzle). Theneedle can have be a standard needle having a diameter between 34 gaugeand 7 gauge, where diameter decreases with gauge size. In someembodiments, multiple needles are used to generate multiple streams ofpolymer jets towards the collectors. The height of the needle or nozzlewhere the polymer jet starts from can be the same or different from theheight(s) of the collector(s). In preferred embodiments, the height ofthe needle is greater than that of the parallel collectors. In oneembodiment, the needle is pointed in a horizontal orientation, and inanother embodiment, the needle is pointed in a vertical orientation. Theangle that the needle is at relative to the horizontal level can be 0°,10°, 20°, 30°, 40°, 50°, 60°, 70°, 80°, or 90°, preferably from a heightno shorter than the height of the collectors. The needles or syringeswhere the needles are attached can be mounted onto a motorized platform,e.g., a stage, a dispenser, to allow for alterations in theconfiguration of the system or movement of the needles.

The polymer solution can be held in a syringe that is controlled by aprogrammable syringe pump known in the art. The gauge of the needle, thespeed that the polymer solution is pushed out from the needle, and thevolume of polymer to be electrospun can be tuned, according to thecomposition and the viscosity of the solution, the configuration of thecollectors, and the desired properties of formed fibers. In someembodiments, multiple needles are used to generate multiple streams ofpolymer jets on the collectors.

The syringe pump can be mounted onto a base atop a motorized stage knownin the art. This controls the motion of the needle in the x directionand the y direction. Moving along an x-direction may position the needlecloser or farther away from the collectors, while moving along ay-direction may position the needle at a constant distance from thecenter-line of the parallel collectors.

The critical field strength required to overcome the forces due tosurface tension of the solution and fotin a jet will depend on manyvariables of the system. These variables include not only the type ofpolymer and solvent, but also the solution concentration and viscosity,as well as the temperature of the system. In general, characterizationof the jet formed, and hence characterization of the fibers formed,depends primarily upon solution viscosity, net charge density carried bythe electrospinning jet and surface tension of the solution. The abilityto form small diameter fibers depends upon the combination of all of thevarious parameters involved. For example, electrospinning of lowerviscosity solutions will tend to form beaded fibers, rather than smoothfibers. In fact, many low viscosity solutions of low molecular weightpolymers will break up into droplets or beads, rather than form fibers,when attempts are made to electrostatically spin the solution. Solutionshaving higher values of surface tension also tend to form beaded fibersor merely beads of polymer material, rather than smooth fibers. Thus,the preferred solvent for any particular embodiment will generallydepend upon the other materials as well as the formation parameters, asis known in the art.

In some embodiments, the electrospun fibers are made under sterileconditions to avoid the need for subsequent sterilization, although mostsutures can be sterilized by means such as ethylene oxide.

Additional elements can be included in the electrospinning system, suchas means for temperature control, for example, a strip heater, fan, or atemperature controller.

One or two motors can be connected to one or both opposing collectors.Generally, a motor has a shaft to allow for connection with specificcollectors via the adaptor. Generally, the motor is capable of providingclock-wise or counter clock-wise rotation up to a speed of 1,000revolutions per minute (rpm), 2,000 rpm, 3,000 rpm, 4,000 rpm, 5,000rpm, 6,000 rpm, 7,000 rpm, 8,000 rpm, 9,000 rpm, 10,000 rpm, or greater.

3. Other Methods to Fabricate Multifilament Fibers.

Other methods may be used to fabricate ultra-thin, twistedmulti-nanofiber sutures with sufficient strength and drug loadingcapacity. In general, thin nanofibers are fabricated and twisted in abundle to compact and strengthen the mechanical properties. Singleneedle single jet, single needle multi-jets, multi-needle multi-jets, oreven needleless configurations for electrospinning may be used tofabricate polymeric nanofibers, which later are twisted by rotating twoends of the bundle of nanofibers in different angular speed and/or indifferent angular directions. Techniques other than electrospinning mayalso be used to fabricate polymeric nanofibers, such as meltblowing,bicomponent spinning, forcespinning, and flash-spinning.

Meltblowing

In a meltblowing process, a molten polymer is extruded through theorifice of a die. The fibers are formed by the elongation of the polymerstreams coming out of the orifice by air-drag and are collected on thesurface of a suitable collector in the form of a web. The average fiberdiameter mainly depends on the throughput rate, melt viscosity, melttemperature, air temperature and air velocity. Nanofibers can befabricated by special die designs with a small orifice, reducing theviscosity of the polymeric melt and suitable modification of themeltblowing setup. To reduce or prevent the sudden cooling of the fiberas it leaves the die before the formation of nanofibers, hot air flowmay be provided in the same direction of the polymer around the die. Thehot air stream flowing along the filaments helps in attenuating them tosmaller diameter. The viscosity of polymeric melt can be lowered byincreasing the temperature.

Template Melt-Extrusion

In template melt-extrusion, molten polymer is forced through the poresof a template (e.g., an anodic aluminum oxide membrane (AAOM)) and thensubsequently cooled down to room temperature. A special stainless steelappliance may be designed to support the template, to bear the pressureand to restrict the molten polymer movement along the direction of thepores. The appliance containing the polymer was placed on the hot plateof a compressor (with temperature controlled functions) followed by theforcing of the polymeric melt. Isolated nanofibers may be obtained bythe removal of the template (e.g., dissolution with appropriatesolvent(s)).

Flash-Spinning

In the flash-spinning process, a solution of fiber forming polymer in aliquid spin agent is spun into a zone of lower temperature andsubstantially lower pressure to generate plexi-filamentary film-fibrilstrands. A spin agent is required for flash-spinning which: 1) should bea non-solvent to the polymer below its normal boiling point, 2) can forma solution with the polymer at high pressure, 3) can form a desiredtwo-phase dispersion with the polymer when the solution pressure isreduced slightly, and 4) should vaporize when the flash is released intoa substantially low pressure zone. Flash-spinning is more suitable fordifficult to dissolve polymers such as polyolefins and high molecularweight polymers. The spinning temperature should be higher than themelting point of polymer and the boiling point of solvent in order toeffect solvent evaporation prior to the collection of the polymer.

Bicomponent Spinning

Bicomponent spinning is a two-step process that involves spinning twopolymers through the spinning die (which forms the bicomponent fiberwith island-in-sea (IIS), side-by-side, sheath-core, citrus orsegmented-pie structure) and the removal of one polymer.

Other Approaches

In some embodiments, the disclosed stent devices may be prepared viaother methods than electrospinning, such as 3-D printing and dipping inpolymer solutions and drying of a cylindrical/wire-shaped template,followed by removal of the template after the polymeric wall of thestent is formed, resulting in a stent device with a wall surrounding alumen.

III. Multifilament Fibers as Sutures or Coatings for Sutures

1. Properties

A. Diameter & Strength

Suture diameters are defined by the United States Pharmacopeia (U.S.P.).Modern sutures range from #2 (heavy braided suture) to #11-0 (finemonofilament suture for ophthalmics). Suitable diameters for ophthalmicuse are USP size 6.0-11.0, preferably 7.0-11.0, more preferably8.0-11.0, most preferably 9.0-11.0.

Absorbable sutures as formed satisfy the strength requirement forabsorbable sutures set forth in the United States Pharmacopeia (Table1).

TABLE 1 U.S.P. specifications for synthetic, absorbable sutures. USPAverage Diameter (μm) Knot-pull Size Min Max Tensile Strength (N) 10-020 29 0.24*  9-0 30 39 0.49*  8-0 40 49 0.69*  7-0 50 69 1.37  6-0 70 992.45  5-0 100 149 6.67  4-0 150 199 9.32  3-0 200 249 17.4  2-0 300 33926.3 *indicates tensile strength is measured by straight pull.

For non-absorbable sutures, strength requirements for different diametersutures are classed on the United States Pharmacopeia, e.g., based onthe type of coating. For example, class I suture is composed of silk orsynthetic fibers of monofilament, twisted, or braided construction wherethe coating, if any, does not significantly affect thickness (e.g.,braided silk, polyester, or nylon; monofilament nylon or polypropylene);class II suture is composed of cotton or linen fibers or coated naturalor synthetic fibers where the coating significantly affects thicknessbut does not contribute significantly to strength (e.g., virgin silksutures); and class III suture is composed of monofilament ormultifilament metal wire.

Non-absorbable sutures as formed satisfy the strength requirement fornon-absorbable sutures set forth in the United States Pharmacopeia(Table 2).

TABLE 2 U.S.P. specifications for non-absorbable sutures (average knot-pull limits of various sizes and diameters of sutures). Limits on Limitson Average Knot-Pull Limits on Average Knot-Pull Average (except whereotherwise specified)^(a) (except where otherwise specified)^(a) DiameterTensile Strength (in kgl)^(b) Tensile Strength (in N)^(b) USP MetricSize (mm) Class I Class II Class III Class I Class II Class IIII Size(gauge no.) Min. Max. Min. Min. Min. Min. Min. Min. 12-0  0.01 0.0010.009 0.001

— 0.002

0.01

— 0.02

11-0  0.1 0.010 0.019 0.006

0.005

0.02

0.06

0.05

0.20

10-0  0.2 0.020 0.029 0.019

0.014

0.06

0.194

0.14

0.59

9-0 0.3 0.030 0.039 0.043

0.029

0.07

0.424

0.28

0.68

8-0 0.4 0.040 0.040 0.06 0.04 0.11 0.59 0.39 1.08 7-0 0.5 0.050 0.0690.11 0.06 0.16 1.08 0.59 1.57 6-0 0.7 0.070 0.099 0.20 0.11 0.27 1.961.08 2.65 5-0 1 0.10 0.149 0.40 0.23 0.54 3.92 2.26 5.30 4-0 1.5 0.150.199 0.60 0.46 0.82 5.88 4.51 8.04 3-0 2 0.20 0.249 0.96 0.66 1.36 9.416.47 13.3 2-0 3 0.30 0.339 1.44 1.02 1.80 14.1 10.0 17.6 0 3.5 0.350.399 2.16 1.45 3.40

21.2 14.2 33.3

1 4 0.40 0.499 2.72 1.81 4.76

26.7 17.8 46.7

2 5 0.50 0.599 3.52 2.54 5.90

34.5 24.9 57.8

3 and 4 6 0.60 0.699 4.88 3.68 9.11

47.8 36.1 89.3

5 7 0.70 0.799 6.16 — 11.4

60.4 — 112

6 8 0.80 0.899 7.28 — 13.6

71.4 — 133

7 9 0.90 0.999 9.04 — 15.9

88.6 — 156

8 10 1.00 1.099 — — 18.2

— — 178

9 11 1.100 1.199 — — 20.5

— — 201

10  12 1.200 1.299 — — 22.8

— — 224

^(a)The tensile strength of sizes smaller than USP size 8-0 (metric size0.4) is measured by straight pull. The tensile strength of sizes largerthan USP size 2-0 (metric size 3) of monofilament Class III (metallic)nonabsorbable surgical suture is measured by straight pull. Silver wiremeets the tensile strength values of Class I sutures but is tested inthe same manner as class III sutures. ^(b)The limits on knot-pulltensile strength apply to nonabsorbable surgical suture that has beensterilized. For nonsterile sutures of Class I and Class II, the limitsare 25% higher.

indicates data missing or illegible when filed

The sutures as formed typically have a diameter between 10 μm and about400 μm, preferably between 10 and about 50 microns, more preferablybetween about 20 and about 50 microns. The sutures typically have aYoung's modulus of at least about 700, 800, 900, 1000, 1100, 1200, 1300,1400, 1500, 1600, 1700, or 1800 MPa. Specifically, as fibers aretwisted, the overall diameter of the multifilament “bundle” generallydecreases, e.g., 500 μm, 400 μm, 300 μm, 200 μm, 150 μm, 100 μm, 50 μm,40 μm, 30 μm, 20 μm, or 10 μm, while the “bundle” is of sufficienttensile strength according to USP standards. Essentially, the more thefibers are twisted, the more compact the composite becomes, and the morefibers that can be packed into a single suture of a specific size. Thisis one of the main reasons twisting increases strength.

In some embodiments, the sutures have the above diameter and a tensilemodulus (e.g., Young's modulus) of at least about 600, 650, 700, 750,800, 850, 900, 950, or 1000 MPa. In particular embodiments, the sutureshave a tensile modulus (e.g., Young's modulus) from about 1000 to about2500 MPa, preferably from about 1200 to about 2500 MPa, more preferablyfrom about 1300 to about 2300 MPa. The sutures should retain the tensilestrength for the requisite period of time.

In some embodiments of drug-loaded sutures, the sutures have a breakingstrength as specified by the USP in Tables 1 and 2 for differentdiameters.

B. Absorbability

In some embodiments, the multifilament fibers are made with absorbablematerials which are broken down in tissue after a given period of time,which depending on the material can be from ten days to one year. Theycan be used in many of the internal tissues of the body. In cases wherethree weeks is sufficient for the wound to close thinly, the suture isnot needed any more, and absorbable multifilament fibers leave noforeign material inside the body and no need for the patient to have thesutures removed. Examples of absorbable polymers are listed asbiodegradable polymers below.

In other embodiments, the multifilament fibers are made withnon-absorbable materials which are not metabolized by the body. They canbe used either on skin wound closure, where the sutures can be removedafter a few weeks, or in some inner tissues in which absorbable suturesare not adequate.

Generally, any polymer can be used in electrospinning to preparemultifilament fibers. For instance, the rhythmic movement in the heartand in blood vessels may require a suture material which stays longerthan three weeks, to give the wound enough time to close. Other organs,like the bladder, contain fluids may make absorbable sutures disappeartoo soon for the wound to heal. Hence, a non-absorbable or a mixture ofabsorbable and non-absorbable materials is used to prepare electrospunfibers and to twist into sutures or coatings for sutures. Examples ofnon-absorbable polymers are listed as nondegradable polymers below.

In an embodiment where the electrospun fibers are used to coat existingabsorbable or non-absorbable sutures or suture thread, the fibers can bemade with degradable or non-degradable polymer.

C. Coating Properties

The multifilament fibers can be used to coat existing sutures to providedesired surface properties. In some embodiments, the coating fibersinclude one or more therapeutic, prophylactic or diagnostic agents thatare encapsulated in the nanofibers, which upon twisting ontonon-agent-eluting suture allows for sustained release of the agent.

In other embodiments, the coating improves glide and reduces irritationand capillarity while still maintaining good knot security. By twistingthe electrospun fibers around a suture, the coating fibers are stillthin enough, do not compromise the strength of the sutures, and do notget easily rubbed off during manipulation. The lower the coefficient offriction, the less the thread gets stuck and injures the tissues. Forinstance, the glyconate, i.e., a copolymer made of glycolide (e.g.,72%), trimethylene carbonate (e.g., 14%), and caprolactone (e.g., 14%),can be used to prepare the electrospun fibers or coated onto thecomposite suture, combining good glideability and/or knot security.

2. Compositions

A. Polymers

In some embodiments, polymers that have been found suitable for use inbiological applications can be utilized. In some embodiments, polymersthat are degradable can be utilized. Non-degradable polymers can beutilized alone, in combination, or in sequence with degradable polymers.

A polymeric solution that is loaded into an electrospinning nozzle orsyringe can include any suitable solvent. Selection of solvent can beimportant in determining the characteristics of the solution, and henceof the characteristic properties of the nanofibers formed during theprocess. Examples include hexafluoroisopropanol, methanol, chloroform,dichloromethane, dimethylformamide, acetone, acetic acid, acetonitrile,m-cresole, tetrahydrofuran (THF), toluene, as well as mixtures ofsolvents.

Preferred polymers including polyhydroxy acids such as poly(lacticacid), poly(glycolic acid) and poly(lactic-co-glycolic acid),polycaprolactone, polydioxanone, as well as combinations of polymers(i.e., poly-1-lactic acid/polyethylene glycol) having a molecular weightbetween 5 kDa and 500 kDa.

Other examples of suitable biodegradable, biocompatible polymers includepolyhydroxyalkanoates such as poly-3-hydroxybutyrate orpoly-4-hydroxybutyrate; poly(orthoesters); polyanhydrides;poly(phosphazenes); poly(lactide-co-caprolactones); polycarbonates suchas tyrosine polycarbonates; polyamides (including synthetic and naturalpolyamides); polyesteramides; other polyesters; poly(dioxanones);polyurethanes; polyetheresters; polymethylmethacrylates; polysiloxanes;poly(oxyethylene)/poly(oxypropylene) copolymers; polyketals;polyphosphates; polyhydroxyvalerates; as well as copolymers thereof.

In the most preferred embodiments, the biodegradable polymer ispolycaprolactone or polyglycolide or a poly-(D,L-lactide-co-glycolide)such as poly-(D,L-lactide-co-glycolide) containing about 55 to about 80mole % lactide monomer and about 45 to about 20 mole % glycolide andpoly-(D, L-lactide-co-glycolide) containing about 65 to about 75 mole %lactide monomer and about 35 to about 25 mole % glycolide. The poly-(D,L-lactide-co-glycolide) can contain terminal acid groups.

The biodegradable, biocompatible polymer can be a polylactic acidpolymer or copolymer containing lactide units substituted with alkylmoieties. Examples include, but are not limited to,poly(hexyl-substituted lactide) or poly(dihexyl-substituted lactide).

The molecular weight of the polymer can be varied to optimize thedesired properties, such as drug release rate, tensile strength andtensile modulus, and degradation for specific applications. The one ormore biodegradable, biocompatible polymers can have a molecular weightof between about 1 kDa and 500 kDa. In certain embodiments, thebiodegradable, biocompatible polymers have a molecular weight of betweenabout 15 kDa and about 300 kDa, more preferably between about 50 kDa andabout 2000 kDa.

Non-degradable polymers include polyurethanes, silicones or siliconelastomers, polyesters, acrylic polymers and copolymers, vinyl halidepolymers and copolymers, polyvinyl chloride, polyvinyl ethers,ethylene-methyl methacrylate copolymers, s, ABC resins andethylene-vinyl acetate copolymers, polyamides such as nylon 66 andpolycaprolactam, polyimides; polyethers, and a biocompatible polymeraccording to claim 1 selected from the group consisting of a combinationthereof.

B. Therapeutic, Prophylactic or Diagnostic Agents

The fibers may include one or more therapeutic, prophylactic, ordiagnostic agents that are blended, encapsulated, conjugated to thepolymer in a solution before electro spinning, or encapsulatedin/conjugated to sustained release nanoparticle/microparticleformulations that are entrapped in between or conjugated with the formedfibers. These may be proteins, peptides, nucleic acid, carbohydrate,lipid, or combinations thereof, or small molecules. Suitable smallmolecule active agents include organic and organometallic compounds. Insome instances, the small molecule active agent has a molecular weightof less than about 2000 g/mol, preferably less than about 1500 g/mol,more preferably less than about 1200 g/mol, most preferably less thanabout 1000 g/mol. In other embodiments, the small molecule active agenthas a molecular weight less than about 500 g/mol. The small moleculeactive agent can be a hydrophilic, hydrophobic, or amphiphilic compound.Biomolecules typically have a molecular weight of greater than about2000 g/mol and may be composed of repeat units such as amino acids(peptide, proteins, enzymes, etc.) or nitrogenous base units (nucleicacids). In preferred embodiments, the active agent is an ophthalmictherapeutic, prophylactic or diagnostic agent.

Representative therapeutic agents include, but are not limited to,analgesic agents, anti-fibrotic/anti-scarring agents, anti-inflammatorydrugs, including immunosuppressant agents and anti-allergenic agents,anti-infectious, and anesthetic agents. Exemplary analgesic agentsinclude simple analgesics (e.g., paracetamol, aspirin), non-steroidalanti-inflammatory drugs (e.g., ibuprofen, diclofenac sodium, naproxensodium), weaker opioids (e.g., combinations including codeine phosphate,tramadol hydrochloride, dextropropoxyphe hydrochloride and paracetamol),and stronger opioids (e.g., morphine sulphate, oxycodone, pethidinehydrochloride). Some examples of anti-inflammatory drugs includetriamcinolone acetonide, fluocinolone acetonide, prednisolone,dexamethasone, loteprendol, fluorometholone. Immune modulating drugssuch as: cyclosporine, tacrolimus and rapamycin. Non-steroidalanti-inflammatory drugs include ketorolac, nepafenac, and diclofenac.Antiinfectious agents include antiviral agents, antibacterial agents,antiparasitic agents, and anti-fungal agents. Exemplary antibioticsinclude moxifloxacin, ciprofloxacin, erythromycin, levofloxacin,cefazolin, vancomycin, tigecycline, gentamycin, tobramycin, ceftazidime,ofloxacin, gatifloxacin, rapamycin; antifungals: amphotericin,voriconazole, natamycin. Exemplary steroids suitable to include in thedisclosed suture include, but are not limited to, testosterone, cholicacid, dexamethasone, lanosterol, progesterone, medrogestone, andβ-sitosterol.

In some embodiments, levofloxacin, moxifloxacin, bacitracin, sirolimus,sunitinib, triamcinolone acetonide, cyclosporine, and dexamethasone areincluded individually or in combination in the formulations.

For ophthalmology applications, active agents can include anti-glaucomaagents that lower intraocular pressure (IOP), anti-angiogenesis agents,growth factors, and combinations thereof for treatment of vasculardisorders or diseases. Examples of anti-glaucoma agents includemitomycin C, prostaglandin analogs such as travoprost and latanoprost,prostamides such as bimatoprost; beta-adrenergic receptor antagonistssuch as timolol, betaxolol, levobetaxolol, and carteolol, alpha-2adrenergic receptor agonists such as brimonidine and apraclonidine,carbonic anhydrase inhibitors such as brinzolamide, acetazolamine, anddorzolamide, miotics (i.e., parasympathomimetics) such as pilocarpineand ecothiopate), seretonergics, muscarinics, and dopaminergic agonists.

Representative anti-angiogenesis agents include, but are not limited to,antibodies to vascular endothelial growth factor (VEGF) such asbevacizumab (AVASTIN®) and rhuFAb V2 (ranibizumab, LUCENTIS®), and otheranti-VEGF compounds including aflibercept (EYLEA®); MACUGEN® (pegaptanimsodium, anti-VEGF aptamer or EYE001) (Eyetech Pharmaceuticals); pigmentepithelium derived factor(s) (PEDF); COX-2 inhibitors such as celecoxib(CELEBREX®) and rofecoxib (VIOXX®); interferon alpha; interleukin-12(IL-12); thalidomide (THALOMID®) and derivatives thereof such aslenalidomide (REVLIMID®); squalamine; endostatin; angiostatin; ribozymeinhibitors such as ANGIOZYME® (Sirna Therapeutics); multifunctionalantiangiogenic agents such as NEOVASTAT® (AE-941) (Aeterna Laboratories,Quebec City, Canada); receptor tyrosine kinase (RTK) inhibitors such assunitinib (SUTENT®); tyrosine kinase inhibitors such as sorafenib(Nexavar®) and erlotinib (Tarceva®); antibodies to the epidermal grownfactor receptor such as panitumumab (VECTIBIX®) and cetuximab(ERBITUX®), as well as other anti-angiogenesis agents known in the art.

In some cases, the agent is a diagnostic agent imaging or otherwiseassessing the tissue of interest. Examples of diagnostic agents includeparamagnetic molecules, fluorescent compounds, magnetic molecules, andradionuclides, x-ray imaging agents, and contrast media.

The active agents may be present in their neutral form, or in the formof a pharmaceutically acceptable salt. In some cases, it may bedesirable to prepare a formulation containing a salt of an active agentdue to one or more of the salt's advantageous physical properties, suchas enhanced stability or a desirable solubility or dissolution profile.

Generally, pharmaceutically acceptable salts can be prepared by reactionof the free acid or base forms of an active agent with a stoichiometricamount of the appropriate base or acid in water or in an organicsolvent, or in a mixture of the two; generally, non-aqueous media likeether, ethyl acetate, ethanol, isopropanol, or acetonitrile arepreferred. Pharmaceutically acceptable salts include salts of an activeagent derived from inorganic acids, organic acids, alkali metal salts,and alkaline earth metal salts as well as salts formed by reaction ofthe drug with a suitable organic ligand (e.g., quaternary ammoniumsalts). Lists of suitable salts are found, for example, in Remington'sPharmaceutical Sciences, 20th ed., Lippincott Williams & Wilkins,Baltimore, Md., 2000, p. 704. Examples of ophthalmic drugs sometimesadministered in the form of a pharmaceutically acceptable salt includetimolol maleate, brimonidine tartrate, and sodium diclofenac.

The agent or agents can be directly dispersed or incorporated into thefibers as particles using common solvent with the polymer, for examplesmicroparticles and/or nanoparticles of drug alone, or microparticlesand/or nanoparticles containing a matrix, such as a polymer matrix, inwhich the agent or agents are encapsulated or otherwise associated withthe particles.

The concentration of the drug in the finished fibers or foamedstructures of fibers can vary. In some embodiments, the amount of drugis between about 0.1% and about 50% by weight, preferably between about1% and about 20% by weight, more preferably between about 3% and about20% by weight, most preferably between about 5% and about 20% by weightof the finished stents.

In particular embodiments, the agent is released at an effective amountto inhibit, prevent, or treat disorders or diseases in ophthalmology,cardiology, or neurology among others for at least 2 weeks, 4 weeks, 6weeks, 8 weeks, 10 weeks, 12 weeks, 16 weeks, or 20 weeks.

The sutures can be modified by inclusion of a hydrophilic polymer suchas PEG or a POLOXAMER® to provide a burst release of an active agent,such as an antimicrobial agent, followed by sustained release over anextended period of time, such as one week, two weeks, 4 weeks, 6 weeks,8 weeks, 10 weeks, 12 weeks, 14 weeks, 16 weeks, 18 weeks, or 20 weeks.

C. Formulations

The amount of polymer or polymers in the finished fibers can vary. Insome embodiments, the concentration of the polymer or polymers is fromabout 75% to about 85% by weight of the finished fibers. In someembodiments, the concentration of the polymer or polymers is from about85% to about 100% by weight of the finished fibers.

Representative excipients include pH modifying agents, preservatives,antioxidants, suspending agents, wetting agents, viscosity modifiers,tonicity agents, stabilizing agents, and combinations thereof. There maybe residual levels of solvent. Suitable pharmaceutically acceptableexcipients are preferably selected from materials which are generallyrecognized as safe (GRAS), and may be administered to an individualwithout causing undesirable biological side effects or unwantedinteractions.

D. Kit or Packaging

In some embodiments, the suture is sterilized and packaged dry or influid, in containers (e.g., packets) so designed that sterility ismaintained until the container is opened. In some embodiments, thesuture is secured to a needle, which is sterilized and packaged.

IV. Methods of Use

1. Sutures

The multi-filament polymeric sutures can be used simultaneously as drugdelivery vehicles and sutures to close wounds in surgery including, butnot limited to, ophthalmology (e.g., antibacterial operations; cornealtransplant; trauma; acanthamoeba keratitis; specialty surgeries),cardiology, vascular surgery (e.g., anastomosis, or grafts), plasticsurgery (e.g., keloids/hypertrophic scar removal; steroid-loaded toprevent scarring after surgery), regenerative medicine (e.g., peripheralnerve regeneration), and pediatric surgery. In the eye, applicationsinclude ones created in ophthalmologic surgery or due to injury ortrauma to the eye. They can also be used to promote vascular or graftanastomosis. The fibers can also be used as sutures for skin wound orinternal tissue, e.g., nerve, heart, bladder etc.

The sutures can be used in a variety of ophthalmic procedures known inthe art. Examples include, but are not limited to, trabeculectomy aswell as pterygium removal, cataract surgery, strabismus correctionsurgery, penetrating keratoplasty, sclerectomy, and conjunctivalclosure.

Trabeculectomy is an ophthalmic surgical procedure used in the treatmentof glaucoma. Removing part of the eye's trabecular meshwork and adjacentstructures allows drainage of aqueous humor from within the eye tounderneath the conjunctiva to relieve intraocular pressure. The scleralflap is typically sutured loosely back in place with several sutures.Common complications include blebitis (an isolated bleb infectiontypically caused by microorganisms such as Staphylococcus epidermidis,Propriobacterium acnes, or Staphylococcus aureus), inflammation, andbleb-associated endophthalmitis.

Endophthalmitis is an inflammation of the ocular cavities and theiradjacent structures. It is a possible complication of all intraocularsurgeries, particularly cataract surgery, which can result in loss ofvision or the eye itself. Endophthalmitis is usually accompanied bysevere pain, loss of vision, and redness of the conjunctiva and theunderlying episclera. Infectious etiology is the most common and variousbacteria and fungi have been isolated as the cause of theendophthalmitis. The patient needs urgent examination by anophthalmologist and/or vitreo-retina specialist who will usually decidefor urgent intervention to provide intravitreal injection of potentantibiotics and also prepare for an urgent pars plana vitrectomy asneeded. Enucleation may be required to remove a blind and painful eye.

Ideally, ophthalmic suture materials are biodegradable or absorbable andbiodegradable over the useful suture lifetime, retaining the requisitetensile strength, mechanical modulus, and capable of deliveringtherapeutic or prophylactic agents to increase patient success. However,it is not essential the suture be biodegradable. For pterygium removal,cataract surgery and strabismus correction surgery, sutures can be usedto close the wound and release antibiotic and anti-inflammatory drugs.For trabeculectomy surgeries, sutures can be placed on sclera flapsproviding local chemotherapeutic agents, decreasing production of scartissue, and on conjunctival closure with antibiotic release. Inpenetrating keratoplasty, the sutures hold the graft, as well as releaseantibiotic and immunosuppressant agents.

2. Coatings

The twisted multifilament fibers can weave around and coat existingsutures or other devices, to provide additional functionality and/orsurface properties. In some embodiments, the coating fibers include oneor more therapeutic, prophylactic or diagnostic agents that areencapsulated in the nanofibers. Two or more populations of fibersincluding different active agents can be twisted and form the coating ona suture, and depending on the sequence of coating and tightness oftwisting, the release profiles for the different active agents arecontrolled and finely tuned.

In other embodiments, the coating improves glide and reduces irritationand capillarity while still maintaining good knot security. By twistingthe electrospun fibers around a suture, the coating fibers are stillthin enough, do not compromise the strength of the sutures, and do notget easily rubbed off during manipulation. Specifically, the lower thecoefficient of friction, the less the thread gets stuck and injures thetissues. For instance, a glyconate, i.e., a copolymer made of glycolide(e.g., 72%), trimethylene carbonate (e.g., 14%), and caprolactone (e.g.,14%), can be used to prepare the electrospun fibers, combining goodglideability and knot security.

3. Other Applications

Mixtures of materials can be electrospun to form composite fibers. Forinstance, a solution including one or more polymers in combination witha non-polymeric additive can be electrospun to form composite fibers.Additives are generally selected based upon the desired application ofthe formed fiber structures. For example, one or more polymers can beelectrospun with a biologically active additive that can be polymeric ornon-polymeric, as desired. By way of example, a 3D structure of fiberscan include an electrospun polymer in conjunction with one or moretherapeutic, prophylactic, and/or diagnostic agent. The secondarymaterial can be incorporated in the fibers during formation as is knownin the art, for example, as described in U.S. Pat. No. 6,821,479 toSmith, et al., U.S. Pat. No. 6,753,454 to Smith, et al., and U.S. Pat.No. 6,743,273 to Chung, et al.

In other embodiments, the ultra-thin, high strength multifilament fiberscan be braided into membranes with defined interstices for industrialapplications, e.g., water purification.

The present invention will be further understood by reference to thefollowing non-limiting examples.

Suture breaking strength, Levo concentration, and bacterial load arepresented as mean±standard error below. Statistical significance forbreaking strength and bacterial load data has been determined viaone-way ANOVA followed by Tukey test. Statistical significance for theKaplan-Meier curve of long-term infection prevention was determined viathe Mantel-Cox test.

Example 1: Formation of Multi-Filament Sutures and Effect of PolymerType

Materials and Methods

Polycaprolactone (PCL), polylactic acid (PLLA), andpoly(lactic-co-glycolic acid) (PLGA, 75:25) used were all at a molecularweight of 80 kDa; polyglycolide (PGA) and polydioxanone (PDO) used werethe only commercially available polymers from Purac: Corbion and SigmaAldrich, respectively.

As shown in FIG. 1, a grounded, drill chuck 270 connected to a motor 250via an adaptor 260 was a collector 204 for electrospun fibers to depositon one end; and a standalone, parallel, grounded stand 202 was used asanother collector for the other end of the electrospun fibers to depositonto. The two grounded collectors, 202 and 204, were situatedperpendicularly to the syringe pump. Rotation of one collector resultedin the twisting of deposited parallel fibers into a single,multifilament suture. The amount of fiber deposition, and consequently,suture diameter could be reproducibly tuned by adjusting spray time.

A 120 W regulated high voltage DC power source 200 applied a voltage toa blunt tip needle 210 on the end of a syringe 220. This allowed for theejection, from the syringe, of electrified polymer solution 230 held inthe syringe 220 and the syringe was controlled for flow rate by aNE-1000 Programmable Single Syringe Pump 240 mounted onto a plexiglassbase atop a motorized stage capable of controlled x- and y-directionmotion. The drill chuck 270 was connected to a mounted 120V, ⅓ hp,300-3,450 rpm speed-control motor 250 (capable of clockwise orcounter-clockwise rotation) via an adaptor 260. Solutions wereelectrospun via pumping at 450 μL/h through a 20 G blunt-tip needle withan applied voltage of 17 kV, at a distance of 13 cm from a set ofparallel grounded collectors to form parallel nanofibers. One collectorwas then rotated clockwise for a specified number of rotations (twists)prior to removal of the suture from the collectors and storage at −20°C.

When a charged polymer jet was ejected from the needle, it deposited inthe air gap between both collectors 204, 202. As the polymer solutioncontinued to be ejected, hundreds of parallel fibers were formed withone end attached to the drill chuck and the other end attached to thestandalone parallel stand.

Next, the drill chuck 270 was rotated about an axis defined bycollectors 204, 202, to twist the parallel fibers into 28 μm-thick indiameter and having 1,575 twists.

The breaking strengths of these sutures made with different polymerswere evaluated. The morphology was examined under scanning electronmicroscopy (SEM).

Suture diameter was determined via light microscopy using the 20×objective of an Eclipse TS100 (Nikon Instruments, Melville, N.Y.) andcalibrated Spot 5.2 Basic imaging software (Spot Imaging, SterlingHeights, Mich.). Each suture was measured at three different locationsat least 2 cm apart, and used in additional experimentation only if theaverage diameter was within ±0.5 μm of the specified diameter.

Suture morphology was observed via SEM at 1 kV using a LEO FieldEmission SEM (Zeiss, Oberkochen, Germany). Prior to imaging, sampleswere desiccated and then sputter coated with 10 nm of Au/Pd (Desk II,Denton Vacuum, Moorestown, N.J.).

Sutures (n=3-4 for each condition) were clamped vertically and thenpulled until breaking at a rate of 2.26 mm/min using a DMA 6800 (TAInstruments, Timonium, Md.).

Results

Hundreds of nano-fibers were twisted in one direction and tightlypacked. As shown in FIG. 2, the multifilament sutures (having an overallthickness of 28 μm after twisting of hundreds of nano-fibers) made fromPCL provided the greatest strength, and surpassed the knot-pull tensilestrength requirement according to USP specifications for 10-0 sutures.This study was performed comparing the listed polymers all of amolecular weight of about 75 kDa. It is believed if other molecularweights of polymers are used, a different polymer composition maypossess the greatest strength after twisting. Scanning electronmicroscopy (SEM) of multifilament sutures confirmed manufacture of ahighly uniform, non-porous, and defect-free thread composed ofnanofibers, where individual nanofibers had a flat, ribbon-shapedmorphology. The flat, ribbon-shaped morphology of the individualnanofibers indicated that the twisting process led to stretching ofnanofibers, which was believed to improve fiber crystallinity andtensile strength.

Multifilament, drug-loaded sutures were cylindrical and met U.S.P.specifications for 10-0 suture diameter (20-29 μm), making them suitablein size for ocular surgery. SEM images showed they were also comparablein both size and shape to commercially available 10-0 Ethilon® (nylon)sutures.

Example 2: Formation of Mono-Filament Sutures and their Strengths

This study was done with monofilament sutures for comparison with thetwisted multi-filament structures described herein.

Materials and Methods

As shown in FIG. 3A, an electrospinning configuration with a singlecollector was used to obtain micro-fibers.

Poly (L-lactic acid) (PLLA) solutions containing levofloxacin anddifferent amounts of polyethylene glycol (PEG) at 1%, 2%, or 4%, or 2%by weight PLURONIC® F127 were electrospun. Briefly, PLLA (221 kDa;Corbion, Amsterdam, Netherlands) at 86-89% (w/w) was mixed withlevofloxacin (Sigma Aldrich, St. Louis, Mo.) at 10 wt % and either PEG(35 kDa, Sigma Aldrich) or PLURONIC® F127 (BASF, Florham Park, 73 NJ)between 1-4 wt % and dissolved in chloroform (Sigma Aldrich) at roomtemperature for 24 h. Levofloxacin concentration was held constant andPLLA concentration in chloroform was maintained at 15 wt % in allformulations. Sutures were produced by wet electrospinning thepolymer/drug solution in a setup consisting of a high voltage powersupply (Gamma High Voltage Research, Ormond Beach, Fla.), syringe pump(Fisher Scientific, Waltham, Mass.), and rotating metal collector withhexane (Sigma Aldrich) as the lending solvent. The polymer solution wasejected through a blunted 18G needle (Fisher Scientific) at 13 mL/h with4.7 kV of applied voltage 5 cm away from the collector rotating at 40rpm. Fibers were then collected and desiccated for two days prior tostorage at −20° C.

15% PCL with 8% Levo was also used at a flow rate of 1 mL/hr and 28 μmin diameter using the same setup.

Following suture manufacture, fibers were desiccated and stored at −20°C. preceding use in additional experiments. Prior to tensile testing,sutures were allowed to fully thaw and were cut into 3 cm segments.

For suture morphology and size assessment, sutures were seriallydehydrated in ethanol (Sigma Aldrich) and dried prior to sputter coatingwith 10 nm of Au/Pd. Samples were then imaged via scanning electronmicroscopy (SEM) at 1-2 kV using a LEO Field Emission SEM (Zeiss,Oberkochen, Germany) and suture diameter measured using ImageJ software(n=14 for each condition).

For tensile strength measurement, mechanical properties of the sutureswere evaluated using a DMA 6800 (TA Instruments, Timonium, Md.). 3 cmlong samples (n=7 for each condition) were clamped vertically and forcefrom a 5 N load cell was applied at 0.05 N/min to stretch the sampleuntil breaking.

For in vitro drug release, 10 mg of suture (n=3) was placed into 10 mLof 1× Dulbecco's Phosphate Buffered Saline (PBS, ATCC, Manassas, Va.)rotating at 37° C. At each time point, 2 mL aliquots were withdrawn andreplaced with fresh PBS. Aliquots were frozen, lyophilized, andresuspended in ultrapure water prior to high performance liquidchromatography (HPLC; Waters Corporation, Milford, Mass.) analysis. 100μL samples were injected into a Waters Symmetry® 300 C18 5 μm columnwith a mobile phase of 0.1% v/v trifluoroacetic acid (Sigma Aldrich) inwater:acetonitrile (75:25 v/v, 98 Fisher Scientific) at a flow rate 1mL/min. Elution was monitored by a 2998 photodiode array detector todetect levofloxacin with excitation at 290 nm and emission at 502 nm.Drug loading was determined by dissolving a 5 mg sample of suture into amixture of tetrahydrofuran (Sigma Aldrich):acetonitrile (20:80) andinjecting into the column under the same conditions as the releasesamples.

For assessment of bacterial inhibition, 1 cm of suture was placed in 1mL of PBS and incubated at 37° C. for 1, 3, and 6 h and 1, 2, 3, 4, 5,6, and 7 days (n=6 for each time point). S. epidermidis (ATCC) wascultured overnight at 37° C. on agar plates produced using nutrient agar(BD, Franklin Lakes, N.J.). At each time point, sutures were retrievedand placed on plated cultures in order to investigate bacterialinhibition. Bacterial inhibition zones around the sutures were measuredand imaged 24 h after suture placement.

For assessment of in vivo biocompatibility, animals were cared for andexperiments conducted in accordance with protocols approved by theAnimal Care and Use Committee of the Johns Hopkins University. Protocolsare also in accordance with the ARVO Statement for the Use of Animals inOphthalmic and Vision Research. 1 mm of 8-0 Ethilon® (nylon), Vicryl®(poly(lactic-co-glycolic acid); PLGA) (Ethicon, Somerville, N.J.) and 4%PEG/PLLA/levofloxacin sutures (n=3) were implanted into the corneas of6-8 weeks old, male Sprague-Dawley rats (Harlan Laboratories, Frederick,Md.). Prior to implantation, rats were intraperitoneally anesthetizedwith a solution of Ketamine:Xylazine (75:5 mg/kg, Sigma Aldrich) and adrop of 0.5% proparacaine hydrochloride ophthalmic solution (Bausch &Lomb Inc., Tampa, Fla.) was applied to the cornea. Followingimplantation, the rats were evaluated for signs of infection every dayfor seven days. The rats were then euthanized and eyes enucleated, fixedin formalin (Sigma Aldrich) for 24 h, embedded in paraffin, crosssectioned, and stained with hematoxylin and eosin for histologicalevaluation.

Results

Electro spinning of a 10 wt % polymer solution with application of 4.7kV into a collector containing hexane and rotating at 40 rpm (as shownin FIG. 3A) allowed for manufacture of a single, uniform, defect-free,cylindrical filament without beading, necking, or pores. Microfibersmanufactured with a collector speed of 40 rpm were thinner than thosemanufactured at lower speeds, and were more uniform in diameter thanthose manufactured at higher speeds where there was also significantfiber loss at the edge of the collector. Under these conditions, it waspossible to produce meters of suture material at a time. PLLA andlevofloxacin served as the core suture components in this Example.

As shown in FIG. 3B and FIG. 3C, the electrospun monofiber containing 2%F127 had a diameter that could be categorized as a 9-0 suture accordingto USP specification, but its strength was about six-fold lower than theclinical strength requirement for a 9-0 suture. Similarly, theelectrospun monofiber containing 1% PEG or 4% PEG had averaged diametersthat could be categorized as a 8-0 suture (i.e., 4% PEG along with theuse of blunted 18G needles and a flow rate of 13 mL/h provided forsutures 45.1±7.7 μm in diameter), but their strengths were about oneseventh of the clinical strength requirement for a 8-0 suture. Theelectrospun monofiber containing 2% PEG had a diameter that could becategorized as a 7-0 suture according to USP specification, but itsstrength was more than ten-fold lower than the clinical strengthrequirement for a 7-0 suture. Tensile strength evaluation determinedthat the 4% PEG/PLLA/levofloxacin formulation also provided the highestbreaking strength, 0.099±0.007 N, of all formulations tested, althoughit was not statistically significant. Interestingly, althoughlevofloxacin and PLLA are both hydrophobic, increasing the concentrationof hydrophilic PEG did not significantly modify suture tensile strength.

Although thin enough to qualify as a 9-0, 8-0, or 7-0 suture, themonofilament suture was unlike multifilament sutures in Examples 1, 3,and 4, the latter ones of which satisfied the clinical strengthrequirement.

As shown in FIG. 3D and FIG. 3E, the inclusion of PEG, especially at 4%,in the PLLA polymer electrospun fibers enhanced the release rate oflevofloxacin from the fibers, which sustained antibiotic release toinhibit S. Epidermidis for at least 7 days in vitro.

Preliminary studies indicated minimal drug release fromPLLA/levofloxacin sutures manufactured via electro spinning. However,the addition of small percentages of PLURONIC® F127 and PEG polymers tothe formulation resulted in significant and sustained release oflevofloxacin in vitro (FIG. 3D). Regardless of the addition to the corepolymer formulation, all modified suture formulations demonstratedinitial burst release in the first 48 h followed by a slow, sustained,and linear release prior to ultimately reaching a plateau. The 4%PEG/PLLA/levofloxacin suture demonstrated the most significant burstrelease and also the highest cumulative release of all formulationstested. This suture formulation was found to have 4% drug loading andlevofloxacin was detected in release media after more than two monthswith approximately 65% cumulative release.

Bacterial inhibition zone experiments were conducted with S. epidermidisto determine whether levofloxacin released from sutures was capable ofeliminating bacteria in an in vitro setting, and how long this effectmight last in vivo. 4% PEG/PLLA/levofloxacin sutures were cut to 1 cm inlength and incubated in 37° C. PBS from 1 h up to 7 days. After eachtime point, the suture was removed from solution and placed in thecenter of an agar plate that had been cultured with S. epidermidis for24 h. PBS, neat drug, and 4% PEG/PLLA sutures were used as controls.Results of bacterial culture indicated PBS and 4% PEG/PLLA did notinhibit bacterial growth, while the 4% PEG/PLLA/levofloxacin suturecreated a 2 cm inhibition zone after 24 h of drug release in PBS. FIG.3E shows that after 7 days in release media, drug-loaded sutures stillprovided bacterial inhibition, confirming that biologically activeantibiotic was being released from the suture in an amount sufficient toeliminate surrounding bacteria.

In order to evaluate the potential clinical value of an absorbable,antibiotic-eluting suture, wet electrospun sutures were implanted intothe corneal stroma of male Sprague Dawley rats. 8-0 Ethilon®, 8-0Vicryl®, and 8-0 4% PEG/PLLA/levofloxacin sutures of approximately 1 mmin length were compared to each other and untreated controls after 7days. Notably, 4% PEG/PLLA/levofloxacin sutures remained in the corneaand maintained integrity through the 7 day period, similar to theETHILONEthilon® and VICRYLVicryl® sutures. Rats were monitored daily,and there were no gross signs of infection or inflammation among any ofthe animals for all sutures tested. Histological analysis showed thatthe tissue reaction to the electrospun 4% PEG/PLLA/levofloxacin suturewas indistinguishable to that of the nylon suture and untreatedcontrols. There were no obvious signs of neovascularization orinflammation in the control, nylon, or antibiotic-eluting sutureconditions. However, immune cell infiltration was apparent in each ofthe rat eyes containing a Vicryl® suture.

Example 3: Effects of Polymer Molecular Weight, Concentration ofPolymer, Duration of Electrospinning, Intensity of Twisting,Concentration/Type of Drug on the Tensile Strength of MultifilamentSutures

A key challenge for translation of drug-loaded sutures to the clinic hasbeen an inability to meet U.S.P. specifications for suture strength.Thus, the impacts of fiber conformation, drug concentration, drug type,and diameter on antibiotic-loaded suture breaking strength wereexamined.

Materials and Methods

The multifilament sutures were prepared using the setup as shown in FIG.1 and followed the procedures as detailed in Example 1. Variations ineither the composition or the amount of twisting of electrospun fiberswere detailed in the description of the Results.

Strength retention test: PCL/8% Levo and PCL/16% Levo sutures (n=5) weresectioned into two halves. The breaking strength of one segment wasmeasured as described in Example 1, while the other segment wassubmerged in 1× Dulbecco's Phosphate Buffered Saline 360 (ATCC,Manassas, Va.) and shaken at 225 rpm at 37° C. for 31 days. Sutures werethen dried prior to measuring breaking strength.

Results

As shown in FIG. 4, among multifilament sutures of 28 μm in diameterformed with twisted fibers (1,575 twists) of PCL at various molecularweights (MWs) and levofloxacin at 8 wt %, the suture from 80 kDa PCLdemonstrated the highest breaking strength. It was not significantlyaffected by loading of 8 (w/w) % levofloxacin. It also satisfied theclinical strength requirement for 10-0 sutures (shown by dash line inFIG. 4).

As shown in FIG. 5, among multifilament sutures of 28 μm in diameterformed with twisted fibers (1,575 twists) of 80 kDa PCL at variousconcentrations and levofloxacin at 8 wt %, 10 and 12 wt % PCLdemonstrated the highest breaking strength, surpassing the clinicalstrength requirement for 10-0 sutures. These were not significantlyaffected by the loading of levofloxacin. Specifically, 8 wt % PCL/Levowas significantly weaker than 10, 12, or 14 wt % PCL/Levo; 10 wt %PCL/Levo was significantly stronger than 14 wt % PCL/Levo; and 16 wt %PCL Levo was significantly weaker than 10 or 12 wt % PCL/Levo.

As shown in FIG. 6A and FIG. 6B, among multifilament sutures formed withtwisted fibers (1,575 twists) of 80 kDa PCL at the optimized 10 wt % andlevofloxacin at 8 wt %, but electrospun deposited at various durationsof time to generate different thickness, 28 μm multifilaments were morethan 2 times stronger than 21 μm multifilaments, although both qualifiedin the size for 10-0 sutures but only 28 μm multifilaments satisfied theclinical strength requirement for 10-0 sutures. 38 μm multifilaments hadeven stronger tensile strength, and having a size as a 9-0 suture, themultifilament composite also surpassed the clinical strength requirementfor 9-0 sutures and was 64% stronger than 28 μm sutures. 9-0 (30-39 μm)and 8-0 (40-49 μm) sutures are also commonly used in ocular surgery. 48μm (8-0) multifilament sutures were also prepared by increasing electrospinning spray time while maintaining 1,575-twist PCL/8% Levo. Suturediameter significantly affected breaking strength 171 in all cases(p<0.05). Decreasing suture diameter from 28 to 21 μm decreased breakingstrength more significantly than increasing Levo concentration from 8%to 40% (comparing FIGS. 6B and 8A), demonstrating the importance ofsuture diameter in the resulting breaking strength of multifilamentsutures. 48 μm PCL/8% Levo sutures, also measured via straight pull,demonstrated a 61% increase in tensile strength in comparison to 38 μmsutures (FIG. 6C).

FIG. 7 illustrates the difference in PCL suture strength with 8% Levo ineither a monofilament or twisted multifilament conformation of identicaldiameter (28 μm). There was an about 50% strength loss with the additionof the drug, Levo, to a monofilament (p<0.001). However, there was nostatistically significant loss in strength with the addition of drug tothe twisted, multifilament composites. The breaking strengths formultifilament PCL suture increased accordingly with the increase innumber of collector rotations (twists). Among multifilament sutureshaving 28 μm in diameter, formed from 80 kDa PCL at the optimized 10 wt% and levofloxacin at 8 wt %, but twisted for different intensities:doubling of twists doubled the suture strength and prevented a strengthloss due to the inclusion of drug. The strength of multifilaments of1,575 twists including 8% Levo and 28 urn in diameter exceeded that ofthe monofilament and surpassed the minimum U.S.P. breaking strengthspecification for 10-0-sized sutures of 0.24 N. Increased twisting alsoresulted in a more compact nanofiber bundle, illustrated by theincreased spray time necessary to manufacture sutures of an equivalentdiameter at a higher number of twists. Thus, increasing the number oftwists allowed for incorporation of a greater number of nanofibers intoa single suture, thereby amplifying breaking strength and increasingdrug loading capacity. Collectively, these factors contributed tomanufacture of drug-loaded, multifilament PCL sutures with unprecedentedstrength.

So far, compared with the monofilaments in Example 3 and FIG. 7, themultifilaments showed that decreasing the individual fiber diameter(e.g., from micro-fiber to nano-fiber) and twisting to create amultifilament composite prevented the loss of strength associated withdrug loading. A monofilament PCL suture lost close to 50% of itsstrength when loaded with drug, but none of the twisted suturessignificantly lost strength with the addition of drugs.

As shown in FIG. 8, among multifilament sutures of 28 urn in diameterformed with twisted fibers (1,575 twists) of 80 kDa PCL at 10 wt % andlevofloxacin at various percents (i.e., drug/polymer (w/w)), loading thedrug up to 24% could still surpassed the clinical strength requirementfor a 10-0 suture, as required by the USP standards for 10-0 sutures.Sutures with 16% or more Levo had a significantly lower breakingstrength (p<0.05) than PCL sutures alone or with 8% Levo. Even withinclusion of 40% Levo into the suture formulation, multifilament PCLsuture breaking strength was significantly higher (p<0.05) than amonofilament suture with 8% Levo, and reached 75% of the U.S.P.specification for a 10-0 suture.

Importantly, both PCL/8% Levo and PCL/16% Levo sutures maintained theirstrengths and demonstrated minimal degradation in vitro over a period of31 days in phosphate buffered saline (PBS), as shown in Table 3.

TABLE 3 In vitro breaking strength retention of PCL/8% Levo and PCL/16%Levo after 31 days. Suture Type Breaking strength retention PCL/8% Levo31 days 96% PCL/16% Levo 31 days 96%

As shown in FIG. 9, multifilament sutures of 28 μm in diameter formedwith twisted fibers (1,575 twists) of 80 kDa PCL at 10 wt % anddifferent drugs (of different hydrophobicity) at 8 wt % all surpassedthe clinical strength requirements by the USP standards for 10-0sutures. Experiment of PCL suture containing 8 wt % rapamycin, in 28 μmdiameter (10-0) from 1,575 twists, also surpassed the breaking strengthrequirement for 10-0 suture. Levofloxacin was considered as arepresentative hydrophobic drug; moxifloxacin was considered as arepresentative hydrophobic drug and is a fourth generationfluoroquinolone that has shown superior potency to Levo; bacitracin wasconsidered as a representative hydrophilic drug from the polypeptideantibiotic class; and tobramycin was considered as a representativeamphiphilic drug, from the aminoglycoside antibiotic classes. Althoughthese antibiotics have different physicochemical properties owing totheir varying molecular structures, there was no significant differencein breaking strength of multifilament PCL sutures loaded with any ofthese molecules (FIG. 9). Importantly, all drug-loaded sutures met bothsize and strength specifications for a 10-0 suture for ocular surgery.The highly crystalline and hydrophobic nature of PCL nanofibersmanufactured through this process likely partitions the drug andpolymer. This may explain the equivalent strength of multifilament PCLsutures without drug and with inclusion of 8% Levo or other antibioticswith disparate molecular structures.

As shown in FIG. 10, levofloxacin contained in the 28 μm-in-diametermultifilament composite formed from 10 wt % 80 kDa PCL/8 wt % Levo with1,575 twists, sustained released for over 350 hours, as analyzed viahigh performance liquid chromatography.

Example 4: Coating a Device (Suture) with Drug-Eluting NanofibersResults in a Coated Suture that Meets USP Size Requirements and AllowsTunable Release without Affecting Strength

Materials and Methods

As shown in FIG. 11, a grounded, drill chuck 370 connected to a motor350 via an adaptor 360 was used as a collector 304, and a standalone,parallel, grounded stand was used as another collector 302. The distancebetween collectors 304 and 302 was denoted as “d”. A 120 W regulatedhigh voltage DC power source 300 was applied to a blunt tip needle 310on the end of a syringe 320. This allowed for the ejection ofelectrified PLLA-PEG solution containing a 20, 40, or 80 wt % rapamycin330 held in the syringe 320. The flow rate of this solution wascontrolled by a NE-1000 Programmable Single Syringe Pump 340 mountedonto a PLEXIGLASS® base atop a motorized stage capable of controlled x-and y-direction motion.

A 10-0, 9-0, or 8-0 nylon suture 390 was fixed on its thread end to thedrill chuck 370. The needle end of the suture was held by the parallelstand 302 where the suture was placed through the stand 302 but this endof the suture was kept free to rotate.

After the charged polymer/drug solution was released, hundreds of thecharged polymer/drug jet deposited between the chuck 370 and theparallel stand 302, surrounding the suture. Due to the electric charge,the fibers are held tightly by the chuck and the parallel stand. Then,the chuck was rotated clockwise to twist these fibers, with the suture“buried” among the fiber Later the chuck was rotated counterclockwise toensure that the suture did not coil or snap, while the coating remainedtight and intact.

Results

As confirmed using SEM, an uncoated 10-0 nylon suture had a smoothsurface and a diameter of approximately 25 μm. The coated 10-0 nylonsuture had hundreds or thousands of nanofibers covering the surface ofthe suture in a compacted, spiral manner. The coating only added about 2μm to about 5 μm to the overall thickness, continuing to meet the 10-0suture size and strength requirement.

FIG. 15 shows the in vitro release of rapamycin from the PLLA/PEGpolymeric nanofibers around a 10-0 Nylon suture was tuned based on theamount of loaded rapamycin in the PLLA/PEG nanofibers around the Nylonsuture.

FIG. 16 shows the strengths of Nylon sutures coated with PLLA/PEGnanofibers containing different amounts of rapamycin were not affectedand still able to meet the U.S.P. requirements.

Overall, nanofiber-coated sutures allow for tunable drug release andloading without affecting suture breaking strength. Coating of 10-0nylon sutures were demonstrated to add a specific amount of fibercoating thickness to the sutures: adding between 3 and 5 μm of fibercoating kept the USP size at 10-0; adding between about 10 and 15 μm offiber coating increased the size to USP 9-0; and adding between about 20and 20 μm of fiber coating increased the size to USP 8-0. For therapamycin release in FIG. 15 from 20% and 40% rapamycin/PLLA/PEG/Nylon(8-0) and the neointimal hyperplasia studies in Example 7, around 20 μmthick fiber coating was added to turn the 10-0 nylon suture into a 8-0suture (with a fiber coating and a nylon core).

Example 5: Biocompatibility Study, and Immediate and Long-TermInhibition Studies of Bacteria in Rat Cornea by Drug-LoadedMultifilament as Sutures or by Sutures Coated with Drug-LoadedNanofibers

Materials and Methods

The biocompatibility of antibiotic sutures was evaluated by implanting 2mm long sutures in 6-8 week old, male Sprague-Dawley rat cornea on day 0and enucleation and fixing on day 2 for histological analysis. Nobacterial inoculation was administered in this biocompatibility study.The implanted sutures and treatment included 10-0 (i) VICRYL® suture;(ii) nylon suture; (iii) nylon suture that was coated with PCLmultifilament fibers containing 8% levofloxacin (PCL/8% Levo/Nylon),(iv) multifilament composite as a suture, made from electrospun from PCLsolution; (v) multifilament composite as a suture, made from electrospunfrom PCL solution containing 8% levofloxacin (PCL/8% Levo); and (vi)multifilament composite as a suture, made from electrospun from PCLsolution containing 16% levofloxacin (PCL/16% Levo). Prior toimplantation, rats were intraperitoneally anesthetized with a solutionof ketamine:xylazine (75:5 mg/kg, Sigma Aldrich) and a drop of 0.5%proparacaine hydrochloride ophthalmic solution (Bausch & Lomb Inc.,Tampa, Fla.) was applied to the cornea. Following implantation, the ratswere evaluated daily for signs of infection, inflammation, orirritation. Two days after implantation, the rats were euthanized andeyes enucleated, fixed in formalin (Sigma Aldrich) for 24 h, embedded inparaffin, cross sectioned, and stained with H&E for histologicalevaluation.

Next, two models of bacterial infections were evaluated in rat corneainjury with suture implantation:

In the first, 2-day model, the cornea of Sprague-Dawley rats werescratched, followed by implantation of sutures and administration of 100μL of Staphylococcus Aureus at 1×10⁸ CFU/mL on day 0. Cornea withoutimplantation or bacteria administration was used as a control(untreated). The implanted sutures and treatment included (i) 2 mmVICRYL® suture, no antibiotic; (ii) 2 mm 10-0 nylon suture, noantibiotic; (iii) 2 mm 10-0 nylon suture and a single drop oflevofloxacin (10 μL of 5 mg/mL, i.e., 0.5%, levofloxacin solution),immediately following implantation of the suture; (iv) 2 mm 10-0 nylonsuture and a daily levofloxacin (three 10 μL drops of 5 mg/mL, i.e.,0.5%, levofloxacin solution each day); (v) 2 mm 10-0 nylon suture thatwas coated with PCL multifilament fibers containing 8% levofloxacin(PCL/8% Levo/Nylon), and (vi) multifilament composite as a suture, madefrom electrospun from PCL solution containing 8% levofloxacin (PCL/8%Levo). At 48 hr after implantation, the following procedures wereperformed: either (a) enucleated the treated eye, removed andhomogenized the cornea and measured bacterial concentration using aplate reader at 600 OD; (b) observed bacterial growth via the streakingmethod by using a sterile swab to wick the top of the rat eye andcultured on agar plates overnight at 37° C.; or (c) enucleated thetreated eye, embedded in paraffin, sectioned, and stained withhematoxylin and eosin.

In the second, 7-day model, S. Aureus was re-administered on day 5 inaddition to the first administration on day 0 as described above toevaluate the capacity of the 10-0 grade multifilament sutures containingeither 8% levofloxacin or 16% levofloxacin, implanted on day 0, tocontinue to prevent ocular infection following the immediatepost-operative period. On day 7, swabs were taken of each corneafollowed by either histological evaluation, bacterial homogenization, orremoval of sutures for examination via SEM (n=4 for each condition). Forthe latter experiment, sutures were removed from the cornea and fixed informalin (Sigma-Aldrich) for 30 min prior to washing with PBS anddehydration with increasing concentrations of ethanol (FisherScientific). Sutures were then imaged.

All animals were cared for and experiments conducted in accordance withprotocols approved by the Animal Care and Use Committee of the JohnsHopkins University. Protocols were also in accordance with the ARVOStatement for the Use of Animals in Ophthalmic and Vision Research.

Bacterial Inoculation and Evaluation in Detail:

Sprague Dawley rats were anesthetized. The operative eye was thenscratched using a 20 G needle (Fisher Scientific) prior to implantationof three 2 mm long nylon (n=12), Vicryl® (n=4), or PCL/8% Levo (n 403=4)suture filaments. 100 μL of 1×10⁸ CFU/mL of S. aureus was thenadministered topically over a period of 10 mins. 10 μL of 0.5%levofloxacin solution was administered topically either oncepost-operatively or three times daily to rat eyes with nylon sutures(n=4, each). Two days after implantation, gross images were taken ofeach eye, prior to swabbing the cornea with a cotton-tipped applicator(Fisher Scientific), and streaking onto tryptic soy agar (FisherScientific) plates. Plates were stored in an incubator at 37° C. for 24h and then imaged. After swabbing the eye, eyes were enucleated andeither prepared for histological evaluation (n=3 for each condition) orevaluated for bacterial load (n=4 for each condition). Briefly, each eyewas placed in sterile tryptic soy broth (Fisher Scientific) andhomogenized using a POWER GEN® 125 homogenizer (Fisher Scientific) for 4min. Samples were then centrifuged at 300 rcf for 5 min, and opticaldensity of the supernatant measured at a wavelength of 600 nm viaspectrophotometry. Infection was confirmed by a positive swab cultureand bacterial load significantly higher than a control eye.

Results

In the biocompatibility study without bacterial inoculation to the eye,histological analysis of tissues (Day 2) surrounding the suturesimplanted in rat cornea showed all antibiotic-loaded sutures werebiocompatible, and did not elicit an influx of innate immune cells tothe site of suture implantation. There were no gross signs ofirritation, inflammation, or infection among any of the treated orcontrol groups for the duration of the study. Histological analysisfurther revealed that implantation of PCL or PCL/Levo sutures did notcause neovascularization, and that the tissue reaction was comparable tocommercially available nylon sutures. Notably, a small ring of cells wasobserved surrounding implanted absorbable Vicryl® sutures.

In the first 2-day model with bacterial inoculation, hematoxylin andeosin (H&E) staining revealed substantial inflammation and cellularinfiltration within the corneas of rats receiving implantation ofVICRYLVicryl® or nylon sutures without post-operative administration ofLevo.

Notably, the concentration of cells was greatest within the immediatevicinity of implanted sutures lacking the antibiotic loading, which wasindicative that the suture itself may be the nidus of infection andlocation of bacterial adherence. Cells were also concentrated aroundnylon sutures implanted in rat eyes receiving a single post-operativedose of Levo. However, there was no sign of infection or inflammation inthe corneal tissue surrounding PCL/8% Levo sutures or nylon sutures inrats receiving three daily doses of Levo, and the tissue resembled thatof a healthy control. Culture of bacterial swabs on agar platessimilarly confirmed the presence of infection in rats with implantationof VICRYLVicryl® or nylon sutures, or nylon sutures followed by a singledose of Levo administered topically.

As shown in FIG. 12, nylon suture that was coated with PCL multifilamentfibers containing 8% levofloxacin (PCL/Levo/Nylon) and multifilamentcomposite as a suture, made from electrospun PCL solution containing 8%levofloxacin (PCL/Levo) both prevented infection, and decreased theamount of bacteria to an amount seen in an untreated control or in thedaily antibiotic regimen. Healthy, control corneas contained a smallamount of endogenous bacteria, the amount of which was not significantlydifferent from the corneas implanted with PCL/Levo sutures or corneasimplanted with nylon sutures receiving three daily drops of Levo.However, a single drop of Levo following implantation of nylon suturessignificantly decreased the bacterial load in comparison to a nylonsuture alone (p<0.05), but was not sufficient to prevent infection. Asevere case of bacterial keratitis was observed in rat eyes with onlyimplantation of a VICRYL® or nylon suture (i.e., implantation ofVICRYLVicryl® and nylon sutures without post-operative treatmentresulted in severe infections characterized by a bacterial load 3.4-4.3times higher than that of a healthy, control cornea); the eyes werehighly inflamed and red, with a whitish hue likely indicating bacterialcolonization and proliferation surrounding the sutures themselves).

In the second, 7-day model where S. Aureus was re-inoculated on day 5,FIGS. 13A and 13B show eyes containing PCL/Levo sutures at either 8% or16% of Levo did not become infected after the initial (day-0) S. aureusinoculation, which was in agreement with the results in the 2-day studyabove. The PCL/Levo multifilament composites with 8% levofloxacin wereable to prevent a second (day-5) infection in 6 out of 8 animals whenassessed on day 7 after implantation (25% of eyes implanted with PCL/8%Levo sutures displayed a minor infection confirmed by bacterial swab andhomogenization). When the concentration of levofloxacin was doubled to16% in the composite sutures (while keeping tensile strength above USPrequirements), it was able to prevent the second infection in 8 out of 8animals (0% of rat eyes containing 10-0 PCL/16% Levo sutures showedsigns of infection throughout this 7-day study). Eyes implanted withnylon sutures on day 0 were only inoculated with S. Aureus 5 days afterimplantation, of which 100% became infected after the single bacterialinoculation on day 5 (also confirmed by SEM images of removed suturesfrom rat corneas 7 days after implantation, showing the presence of S.aureus on all nylon sutures with vast amounts of biofilm formation). SEMimages of removed sutures from corneas after 7 days also revealed somedetectable, but less apparent S. aureus on PCL/8% Levo than on plainNylon sutures, and no apparent S. aureus on PCL/16% Levo sutures. Thesesin vivo results of the double-bacterial challenge experiments werebelieved to demonstrate a significant and sustained drug release overthe period of 1 week.

Example 6: Pharmacokinetics of Levofloxacin (Levo) Delivered fromSutures

Materials & Methods

In order to determine the duration and concentration of Levo deliveryfrom sutures in vivo, a pharmacokinetic study was performed byimplanting three 2-mm-in-length 28 μm PCL/8% Levo and PCL/16% Levosutures into rat corneas.

PCL/8% Levo and PCL/16% Levo sutures were implanted into Sprague Dawleyrat corneas as described above (n=4 for each formulation at each timepoint). At 15, 60, and 120 min, and at 1, 3, 7, and 14 days, aqueoushumor was collected from each eye, followed by removal of implantedsutures and harvesting of the cornea. Tissue and aqueous humor sampleswere weighed immediately after harvesting. Corneal tissue samples werehomogenized in 100 μL to 150 μL of PBS prior to extraction. The standardcurve and quality control samples were prepared in PBS as a surrogatematrix for both aqueous humor and homogenized tissue. Levofloxacin wasextracted from 15 μL of aqueous humor or tissue homogenate with 50 μL ofacetonitrile containing 1 μg/mL of the internal standard,moxifloxacin-d4 (Toronto Research Chemicals, Canada). Aftercentrifugation, the supernatant was then transferred into autosamplervials for LCMS/MS analysis. Separation was achieved with an AGILENTZORBAX® Agilent Zorbax XDB-C18 (4.6×50 mm, 5 μm) column withwater/acetonitrile mobile phase (40:60, v:v) containing 0.1% formic acidusing isocratic flow at 0.3 mL/min for 3 minutes. The column effluentwas monitored using an AB SCIEX® Sciextriple Quadrupole™ 5500mass-spectrometric detector (Sciex, Foster City, Calif.) usingelectrospray ionization operating in positive mode. The spectrometer wasprogrammed to monitor the following MRM transitions: 362.0→318.0 forlevofloxacin and 406.1→108.0 for the internal standard, moxifloxacin-d4.Calibration curves for levofloxacin were computed using the area ratiopeak of the analysis to the internal standard by using a quadraticequation with a 1/×2 weighting function using two different calibrationranges of 0.25 to 500 ng/mL with dilutions up to 1:10 399 (v:v) and5-5,000 ng/mL.

Results

As shown in Table 4, analysis of Levo concentration in harvested aqueoushumor and corneas revealed a burst release of antibiotic followingsuture implantation and for multiple hours afterwards. The Levo releaseprofiles were similar in eyes implanted with either 8% or 16% Levosutures. However, eyes with PCL/16% Levo sutures contained higherconcentrations of Levo in both the aqueous humor and cornea at almostall time points. Sutures maintained their location and macroscopicstructure throughout the course of the study, and in both 8% and 16%Levo conditions, Levo was detected in the cornea and aqueous humor 14days after implantation. HPLC analysis of dissolved sutures revealedLevo loading of 80 and 161 μg/m, respectively, for 8% and 16% Levosutures. A burst release of antibiotics may be important for preventionof immediate post-operative infection when wounds or surgical incisionsare most vulnerable to bacterial infiltration. Herein, local antibioticdelivery from drug-loaded sutures may preclude issues of patientcompliance with topical eye drops, prevent suture-related infectionsthat lead to treatment failure and re-intervention, reduce the need fororal antibiotic use, decrease the risk of infection associated withimplantable ocular devices, and serve as an alternative to the more than12 million nylon sutures used in ocular procedures each year.

TABLE 4 Levofloxacin concentrations in rat corneal tissue and aqueoushumor, following implantation of 2 mm multifilament sutures below,determined via LC-MS. PCL/8% Levo PCL/16% Levo Aqueous Aqueous TimeHumor Humor (hr) (ng/mL) Cornea (ng/g) (ng/mL) Cornea (ng/g) 0.25 4,125± 153   23,167 ± 5,714  4,650 ± 596   40,676 ± 1,875  1 3,503 ± 433  20,937 ± 2,398  5,145 ± 444   27,998 ± 3,690  2 1,877 ± 172   8,793 ±1,528 4,144 ± 485   26,048 ± 4,518  24 54.5 ± 16   261 ± 47  122 ± 41 627 ± 214 72 12.3 ± 2.8  8.2 ± 0.6 33.8 ± 21   14.5 ± 5.6  168 133.9 ±105   87.9 ± 58   210.9 ± 150   93.1 ± 63   336 2.1 ± 1.5 5.3 ± 0.6 3.3± 2.0 3.0 ± 0.4

In vitro levofloxacin release assay from multifilament sutures showeddrug release profile did not change as PCT/Levo suture size increased(Table 5) and sustained release was achieved with PLLA/Levo suture(Table 6).

TABLE 5 In vitro release of levofloxacin from multifilament PCL suturesof various sizes. 10-0 Release (ug) 9-0 Release (ug) 8-0 Release (ug)Time 8% 16% 8% 16% 8% 16% (h) Levo Levo Levo Levo Levo Levo 0.25 1.0412.766 2.273 3.505 3.346 6.064 0.50 0.054 0.137 0.057 0.110 0.186 0.4221.0 0.021 0.022 0.016 0.023 0.081 0.247 2.0 0.010 0.009 0.018 0.0140.029 0.061 24 0.007 0.007 0.008 0.009 0.009 0.014

TABLE 6 In vitro release of levofloxacin from multifilament PLLA suturesover 35 days. 10-0 Release (ug) Time (days) PLLA/8% Levo 0.17 0.1365 10.0075 5 0.0061 7 0.0026 9 0.0022 11 0.0018 14 0.0034 17 0.0016 220.0024 25 0.0018 28 0.0020 35 0.0077

Example 7: Inhibition of Neointimal Hyperplasia in Rat VascularAnastomosis Procedure by Sutures Coated with Drug-Loaded Nanofibers

Materials and Methods

The abdominal aorta of a rat was sectioned and interrupted suturing wasperformed to tie the vessels back together. The sutures used in thisprocedure included (i) 8-0 nylon suture, (ii) nylon suture coated withPLLA/PEG containing 20% rapamycin (8-0), or (iii) nylon suture coatedwith PLLA/PEG containing 40% rapamycin (8-0). Following the coatingprocess, the size of the sutures (ii) and (iii) was within the 8-0 sizerange. Overall suture diameter was increased for about 20 μm with theaddition of fiber coating, i.e., suture diameter increased from 10-0 to8-0 classification. After two weeks, the aorta was harvested, sectionedand stained for histological analysis, where the neointimal hyperplasiaformation was quantified.

Suture Fabrication:

Polymer solutions were made via dissolution of PLLA (221 kDa; Corbion,Amsterdam, Netherlands), PEG (35 kDa; Sigma Aldrich, St. Louis, Mo.),and rapamycin (LC Laboratories, Woburn, Mass.) in hexafluoroisopropanol(Sigma-Aldrich) by shaking overnight at room temperature. Polymer tosolvent concentration was maintained at 10.8% and PEG to PLLAconcentration was maintained at 3.9% for all formulations. Rapamycinconcentration was 20%, 40%, or 80% in regard to PLLA for the 20%Rap/PLLA/PEG, 40% Rap/PLLA/PEG, and 80% Rap/PLLA/PEG formulations,respectively. Prior to electrospinning, the non-needled end of a 10-0nylon suture (Ethicon, Somerville, N.J. or AROSurgical Instruments,Newport, Calif.) was placed into the rotational collector. The needledend was driven through the hole in the opposing collector and allowed tohang loosely. Rap/PLLA/PEG solutions were then pumped through a 20 Gblunt-tip needle at 1 mL/h with an applied voltage of 15 kV at adistance of 17 cm from the parallel, grounded collectors. The collectorcontaining the non-needled end of the suture was then rotated clockwisefor five minutes at 150 rpm and counter-clockwise for 30 s at anidentical speed. The suture was then removed from the collectors andstored at −20° C.

Suture diameter was determined via light microscopy (Eclipse TS100,Nikon Instruments, Melville, N.Y.) and calibrated imaging software (Spot5.2 Basic, Spot Imaging, Sterling Heights, Mich.). Each suture wasmeasured at four different locations at least 2 cm apart, and used infurther experimentation only if the average diameter was between 46 and49 μm, qualifying as an 8-0 suture.

Results

Both quantitatively and qualitatively, increasing rapamycinconcentration significantly decreased the formation of neointimalhyperplasia and the potential occlusion of the vessel. A degradable,drug loaded polymer fiber coating on a traditional nylon suture couldreduce neointimal hyperplasia formation in vascular anastomosissurgeries.

FIG. 14 shows all drug-coated sutures significantly decreased neointimalhypoerplasia. Histology analysis of abdominal aorta at the anastomosison day 14 showed sutures loaded with 40% rapamycin decreased neointimalhyperplasia by 25% compared to 8-0 Nylon sutures alone.

1. A suture comprising a plurality of fibers, the fibers comprising abiocompatible polymer and one or more therapeutic, diagnostic, orprophylactic agents, wherein the plurality of fibers are twisted orbraided in a bundle to form multifilament suture, wherein the suture hasa size and a tensile strength necessary to meet the United StatesPharmacopeia (U.S.P.) criteria.
 2. The suture of claim 1, wherein thesuture has a diameter between 20 μm and less than 30 μm and a tensilestrength greater than 0.24 N.
 3. The suture of claim 1, wherein thesuture has a diameter between 30 μm and less than 40 μm, and a tensilestrength greater than 0.49 N.
 4. The suture of claim 1, wherein thesuture has a diameter between 40 μm and less than 50 μm, and a tensilestrength greater than 0.69 N.
 5. The suture of claim 1, wherein thesuture has a diameter between 50 μm and less than 70 μm, and a tensilestrength greater than 1.37 N.
 6. The suture of claim 1, wherein thetherapeutic or prophylactic comprises an analgesic agent, ananti-glaucoma agent, an anti-angiogenesis agent, an anti-infectiveagent, an anti-proliferative agent, an anti-inflammatory agent, ananti-scarring agent, a growth factor, an immunosuppressant agent, ananti-allergic agent, or a combination thereof.
 7. The suture of claim 1,wherein the biocompatible polymer is selected from the group consistingof polyhydroxyacids, polyhydroxyalkanoates, polycaprolactones,poly(orthoesters), polyanhydrides, poly(phosphazenes), polycarbonates,polyamides, polyesteramides, polyesters, poly(dioxanones), poly(alkylenealkylates), hydrophobic polyethers, polyurethanes, polyetheresters,polyacetals, polycyanoacrylates, polyacrylates, polymethylmethacrylates,polysiloxanes, poly(oxyethylene)/poly(oxypropylene) copolymers,polyketals, polyphosphates, polyhydroxyvalerates, polyalkylene oxalates,polyalkylene succinates, poly(maleic acids), and copolymers thereof. 8.The suture of claim 1, wherein the biocompatible fibers further comprisea hydrophilic polymer.
 9. The suture of claim 8, wherein the hydrophilicpolymer is a polyalkylene oxide selected from the group consisting ofpolyethylene glycol, polyethylene oxide-polypropylene oxide copolymer,or combination thereof.
 10. The suture of claim 1 wherein thebiocompatible polymer comprises polycaprolactone, polydioxanone,polylactide, polyglycolide, polylactide-co-glycolide, polyethyleneglycol, or a copolymer thereof.
 11. The suture of claim 1, wherein thebiocompatible polymer comprises polycaprolactone,polylactide-co-glycolide, polydioxanone, polyglycolide, polyethyleneglycol, or a copolymer thereof, and the therapeutic, diagnostic, orprognostic agent comprises moxifloxacin, levofloxacin, bacitracin,tobramycin, or a combination thereof.
 12. The suture of claim 1, whereinthe polymer comprises polycaprolactone, polylactic acid,polylactide-co-glycolide, polydioxanone, polyglycolide, polyalkyleneglycol, or a copolymer or combination thereof and the therapeutic,diagnostic, or prognostic agent comprises rapamycin, tacrolimus,everolimus, paclitaxel, or a combination thereof.
 13. The suture ofclaim 1, wherein the suture releases an effective amount of thetherapeutic, prophylactic, or diagnostic agent for at least 7 days. 14.The suture of claim 1 comprising a coating.
 15. The suture of claim 1,wherein the fibers coat around another suture, thread or device.
 16. Thecoating of claim 15, wherein the coating releases an effective amount ofthe therapeutic, prophylactic, or diagnostic agent for at least sevendays.
 17. A method of sealing or closing a surgical incision or a wound,comprising closing the incision or the wound with a suture of anyclaim
 1. 18. A method of making the suture of claim 1 comprisingtwisting or braiding a plurality of polymeric nanofibers.
 19. The methodof claim 18 wherein the fibers are twisted or braided around a suture,thread or device.
 20. The method of claim 18 wherein the polymericnanofibers are spun from one or more jets into one or more collectors.21. The method of claim 18 producing twisted or braided fibers havingthe sizes and strength requirements necessary for the United StatesPharmacopeia #2-0-#7-0 sutures.
 22. The method of claim 18 producingtwisted or braided fibers having the sizes and strength requirementsnecessary for the United States Pharmacopeia #8-0, #9-0, and #10-0sutures.